So the other day, i was driving down the freeway with the ac off. all of a sudden, i feel a BOOOM right under me, and i see something fly out from under my car

i take it to a shop, and they said that the AC compressor is bad, and that little front plate off of it basically broke off, probably because the guy that did my ac job didnt screw it back in properly (i paid 50 bucks to convert the ac system and recharge). but the funny thing is...
THE FAN/AC WHATEVER IT IS WILL NOT TURN OFF! even when the fan is off, ac is not off, air blows out of the vents. i cant figure out why!!!! so i just keep it on defrost, and my defrost is on 24/7 haha. is this a big problem? im planning on replacing my ac compressor next weekend, has anyone ever encountered this problem before? thanks!