dash vents not working, all others do on 1997 Chevrolet Suburban 1500

i had a piece fall off on my foot and now my dash vent does not work, took it in and they said something about a box or arm or something. couldn't pinpoint which of the 4 boxes it could be.

Sounds like a Heater Ventilation vacuum motor fell off. If you can find the part then you can show it too a GM parts guy and he/she can help you out and show you on a diagram where it goes. Good Luck!