Steam would tend to revert back the hidden score points determining a rank, when a hacker is caught. This is so, because many people used to pay a hacker, or play with a friend with hack, to rank themselves up. There has been instances of 4 legit (no hacks) people playing together with a hacker (and paying them) to rank up.
So, for quite some time now, If you have been playing with a hacker (regardless of you knowing him or not) and they were caught cheating, the points received would be reverted. If you had ranked up, you'd be deranked to your rank before that game.
Similarly if you had played against a hacker and lost, and then they got banned, you'll get your game loss erased and not count towards your rank.
Basically it would be as if the game with the hacker never happened, nothing more.
I'm sure you'll agree the above is quite fair to both sides. If you had lost against a hacker, its fair that the loss doesn't count, and you don't lose rank because of this. If you had played with a hacker, unwillingly you had an advantage and the win shouldn't really count.
My best guess is the system got confused as the game in question, in your case may have been played a while back or it were more than one game, or something like this (like you lose your rank when you haven't played for a long time) But fear not, I'm pretty sure once you get a victory you'll get your old rank back, with no repercussion to you, whatsoever.
Best Answer
As long as you don't have PowerShell active and running while you're playing, you're fine and the issue is somewhere else. PowerShell is basically a fancy CMD and COULD be used to tamper with the game and inject stuff (hacks). I'm going to go ahead and assume you didn't have PowerShell running while playing, because you'd have to be the one starting PowerShell, so that's not the issue.
Moreover PowerShell is part of Windows; as I said, it's a fancy CMD (hopefully you know what that is, you have 10k on OF, you know what that is :D) and you can't exactly get rid of it that easily.
Just in case do a Ctrl+Shift+Esc and check if its in there in the list, and if it is - Right Click -> End Task.
If this is the first time you get disconnected like so and this has not happened before while you were playing, try restarting your Computer. If this doesn't work, check out your most recently installed apps. Most likely one of those is the problem.