Hey, I was working on my 2005 ZR2 Blazer replacing the spark plugs and this vacuum hose seems to have broken off somewhere but we can't find where it plugs back in.

 

There is a vacuum canister in the fender behind the ABS module. That hose connects to it. if you feel around on the fender right next to the ABS module on the firewall side you should feel a nipple that that hose will connect to. It is very hard to see.

 

willing to bet your AC controls are not working properly either

 

Suggest you replace that vacuum line while you're at it. End looks flared and will likely come off.