Chirping is for the birds

TD and I woke up to chirping, but not the birds. Decided it must be the smoke detector in the hallway, so after she left I took the cover off. Surprise it didn't have a battery. I did some Internet research and found out that some smoke detectors are wired into AC. Remembering that the AC guys had caused the smoke detector to go off and discovering that it was gone, I called them. Meanwhile annoying chirping continues. I checked all the others just to be sure chirping wasn't coming from one of them. It had to be the one in the hallway by the sliding doors to the back porch. After more research....sometimes if they are dirty, they chirp. In removing the cover to clean it, I pulled one side out of the ceiling. Staring at the dangling smoke detector and contemplating its repair, I get a phone call from AC company. Repairman left the smoke detector on the back porch....