When they are at the baggage office, no doubt they came in on an earlier flight.
If your bag comes off last, it was loaded before all the others and it was WAY in the back!

I waited and waited and waited for my luggage and it never appeared from the flight I was on. On deplaning my connecting flight to IAH I was told my connecting Flight from IAH to Cancun had departed several times by several agents directing deplaning passengers to their connecting gates. When everyone else had gotten their luggage in Cancun, I started looking around and found that it had arrived on the flight I was suppose to be on, and was told the flight had departed, but the luggage made it in time! Had to really work it to get the last flight out for the night!
My lesson was never to listen to the Gate assistants and to go to the gate of my connecting flight! @:-)

One of the few times, that CO failed me and created problems with a friend waiting for me at the hotel in Cancum and they could not find my reservation there!