This is an exploitable bug called "The Negative Time Glitch". It occurs when you already have an explorer who is about to find an item shortly, and you deploy a second (or more;)) explorers. They hijack the timer, and also are rewarded with an item. The timer, however, for them, since they just got out of the gate hasn't quite started yet, and is registered as a negative number. Basically, they are being rewarded as if they had been out for the maximum amount of time. It's hard to replicate, you got lucky!
A lot of people are experiencing this issue, and I believe there's no way to restore your vault, as the crash happens due to corrupt save file (it becomes 0kb). The only way to play the game again is to reinstall it and start over. But the crashes will still be happening. I was in the same situation as you, and was very frustrated at first... Lost two vaults to these crashes. But there is a solution! =)
Right now I'm using an app to backup the saves, and whenever the game gets corrupted - I simply restore the previous backup. Here's the app: https://play.google.com/store/apps/details?id=net.fosrollback.fosrollback
Just make a backup EACH TIME BEFORE you start the game (don't rely on auto-backup, it's crap). This way if it gets bugged, you will be able to restore it from the closest point. And try to stick to short sessions, the longer you play non-stop - the more chance that it will get bugged.
And don't worry about losing that stuff you had in the old vault. In a few days it will seem unimportant, it will all come back quickly, and much more. Actually there's a bonus to this app (some advice on tactics from my personal experience, don't read further if you prefer learning everything yourself, and making your own mistakes=)). If you wish, you can backup the save before you open a lunchbox, and if it gives you crappy stuff - just restore and open it again=) Repeat untill it gives you some legendary weapon, like Fat Boy, then equip a dweller with it and send him out, packed with as much stimpaks and radaways as possible. He will bring you so much loot, that you will have to build more storages to keep it all=)
Also make sure to keep your dwellers count under 30 (29 idealy), until you gather enough loot, level them up and equip them with good enough weapons. Because when you reach 30 dwellers - the molerats will start digging their way into your rooms, and you'd better be ready for them... And don't build the radio-station, untill you want to grow the population over 29 dwellers.
Best Answer
Yes there is:
Successfully Rushing will give you the room’s regular rewards plus a special bonus!
Assign Dwellers to production rooms to obtain resources.
Rooms run on Power. Dwellers run on Food and Water.
Dwellers with high Strength perform better on Power rooms.
Dwellers with high Perception perform better in Water rooms.
Dwellers with high Agility perform better in Food rooms.
Build a Medbay to produce Stimpaks.
Build a Science Lab to produce RadAways.
Upgrading a room will make it more efficient and give you more storage.
The Weight Room will allow you to train a Dweller’s Strength.
The Armory room will allow you to train a Dweller’s Perception.
The Fitness Room will allow you to train a Dweller’s Endurance.
The Lounge will allow you to train a Dweller’s Charisma.
The Classroom will allow you to train a Dweller’s Intelligence.
The Athletics Room will allow you to train a Dweller’s Agility.
The Game Room will allow you to train a Dweller’s Luck.
Build Storage Rooms to increase your Vault’s Weapon and Outfit holding capacity.
There are higher tier versions of the production rooms that are more efficient, but more expensive.
If you are out of building space on a floor, build an elevator to access lower parts of your Vault.
Build Medbays and Science Labs to increase your limit of Stimpaks and RadAways.
Rooms farthest from a power source will shut down first.
The longer a Dweller survives in the Wasteland, the better gear they will find.
When a room finishes production, you have a chance to get bonus CAPS based on the Dwellers
Tap a Dweller’s SPECIAL chart for more details.
During a Raider attack, flashing resource bars means they are stealing your resources!
When a Dweller is assigned to the Radio room it will increase all Vault Dwellers happiness.
You can rename a Dweller by tapping their name on the Dweller information pop-up.
You can skip 1 Objective each day by tapping the X on the Objective screen.
If a room is full of Dwellers, the Dweller with the lowest stat for that room will swap places with the new Dweller.
You can get free Lunchboxes for completing some Objectives.
Confused how something works? Check the VDSG in the Pip-Boy for help.
You can assign Dwellers to the Vault entrance to act as guards.
Upgrading your Vault entrance will make it harder for Raiders to break in.
Need extra CAPS? You can sell weapons and outfits from your Vault storage.
Higher level Dwellers with high SPECIAL have a better chance of surviving in the Wasteland.
You can sort the Dweller list by tapping on the column names.
Tap on the resource bars at the top of the screen for more details on your resource storage.
Your Dweller does not suffer damage or radiation when returning from the Wasteland.
Each SPECIAL stat increases a Dweller’s effectiveness in the Wasteland in its own way.
To quickly check on your Dwellers exploring, just tap directly on the Wasteland.
Raiders can strike any time, be sure to have Dwellers ready and on guard!
Radio rooms attract new Dwellers and improve the happiness in your Vault.
A nuclear winter is cold, keep warm with Vault-Tec!
Vault-Tec. We’ll be there! Vault-Tec.
Mr. Handy can help with incidents and Raider attacks.
Send Mr. Handy to the wasteland to collect CAPS.
Opening the vault door or broadcasting from the radio room greatly increases the odds of a Deathclaw attack.
Source: Google Docs "Fallout Shelter Efficiency Data"
Source: REDDIT