When starting the vehicle is revs to 6000 RPMs?

Okay, so here’s the situation: Friday roommate borrowed my car at some point while he had the car he managed to engage the emergency break without realizing it or so he says by the time he got it back to the house the rear wheels had smoke just pouring out of them from all, but cooking the rear brake shoes and wheel bearings. I spent this weekend taking care of replacing those and getting that all fixed but the other issue that I can’t figure out is that now when I go to start the vehicle it’s revving at 6,000 RPMs and it’s not coming down at all. I replaced the IAC yesterday thinking that maybe that was the problem. The throttle body is completely clean as I clean that yesterday when I replaced the IAC there are no vacuum leaks that I can see this may be stupid of me, but there’s a part of me that is wondering if because of him driving with the emergency break engaged for as long as he did is it possible that the computer adjusted its readings thinking that it’s supposed to be putting out that kind of power even though the emergency break isn’t engaged now if that makes sense, I don’t know. I’m just completely dumbfounded and any help you can give would be greatly appreciated. I forgot to mention that the master cylinder was damn near bone dry when he got back, I’m assuming from driving with the emergency break engaged but wasn’t aware whether or not that could have done damage to the brake booster and if it did that possibly cause the issue.