On a recent flight, I was in the unfortunate situation of spending too much time at the lounge and boarding late when I had seat assignment of 2E on an A320. I didn't board extremely late ~ 15 minutes before departure time. There was no overhead bin space until row 31. Every single overhead bin space was occupied. I didn't want to check my bag, so I decided to place my bag over row 31 and decided I would wait until all coach passengers deplaned before making the trek all the way back to row 31 to retrieve my rollaboard.

Did a coach passenger put his/her rollaboard bag in the F class overhead bin? I don't know, although it is quite possible. I didn't track every single passenger removing their bag from the F overhead bin upon deplaning, as I just figured I am going to wait until everyone in Y deplanes first.

However the following day, I was flying on AA F. A coach passenger was going to use the F overhead bin space. But the FA stopped the passenger saying there was still one F passenger that hasn't boarded and she wanted to save the space for him/her. The F passenger boarded late and he started searching for overhead bin space. When I told him that the FA saved some overhead space for his bag, he was very much thankful for what had happened.