Is That Seat Saved?

Although it's often polite to ask if a seat is taken, I often just sit down in any open seat on the bus as long as nobody appears to be saving it. This morning, a picked a seat on the aisle next to a young lady that didn't appear to be saving the seat. As I turned around and sat down, I see the gentlemen following me in the isle kind of look at the girl, then to me, and kind of awkwardly turn around to find a different seat right next to him. It appeared to me that he wanted to have the seat that I had just assumed. He turned around rather awkwardly at me several times through out the bus ride to see that I was still occupying that seat. Sorry dude, next time call shotgun.