Fallout Shelter Restore Mr Handy Purchase

The only thing which could explain it (besides a bug) is that you may missing some electricity or water. If you haven't enough electricity your food and water supply will fall down and maybe collapse. This will increase the radiation of your dwellers. In some cases they may die on this.

Otherwise, I would say it could be a bug. I've had a situation which was nearly the same. In my case electricity was too low, which leads to the situation I described above.

Ok, let's see what Mr. Handy can do:

1. He can collect resources from the floor he's assigned to
2. He can be used as helper in case of room emergencies (fires, bugs, rat moles)
3. He can be used as defender when raiders or deathclaws attack. Advantages are that he's tough, he doesn't count as a dweller so you can have now 7 defenders in one room, he'll travel to the room automatically (if it's on his floor), so you don't have to assign him manually, like a dweller
4. He can explore the Wasteland but can only collect caps (but he's very good at collecting caps)
5. He doesn't gain experience (doesn't levels up)
6. He cannot be healed with stimpacks
7. He can die
8. He can be revived using caps exactly like a dweller (but costs around 2000 caps)
9. He is vault specific. Cannot be shared between your vaults.

That's pretty much it about Mr Handy.

TL/DR: Mr. Handy cannot pick loot while exploring, only caps.