no heat after installing new cd player

[pdub42]

ok so i think its a 1998 hyundai elantra it is my friends. it had an aftermarket stereo in it and we took it out and replaced it with a new one. During the process of pulling the center part of the dash out we must have pulled it out too far and broke something on the heat because it no longer works. We took it back out and looked at it and the gear on the back of the knob that pulls the wire in and out was missing so I set the wire manually to hot just so he has heat until we get another gear but the heat still doesnt work. Checked with it set both directions and no heat. Then looked under the dash were the cable leads to another lever and tried it with that lever in both directions and still no heat. (the car was already warmed up too by the way) upon taking out the dash one more time to look at it a lever of some sort falls out that has broken off of somewhere but we dont know where and it doesnt look like it would go anywhere on the actual hot cold knob itself or anywhere on that cable so is there another cable? or some other kind of control back behind there that this lever would have fallen off of? we would like to get this fixed soon because it is getting very cold out and no heat is not very much fun