Context: I am waiting for DS1 in a busy seating area at gym/trampolining. There are lots of tables most occupied by toddlers/ mums. DS2 (8) and I usually try and grab an arm chair/sofa, there are only 9 of these seats in total, and read quietly. When we arrived there was a free arm chair which DS2 nabbed. Next to it was another armchair with a bag on it. I left it a minute or two then asked everyone on surrounding tables and sofa if the bag belonged to them. It didn't. I moved the bag onto the arm of the chair and sat in the chair. All good. 15 min later a man pushed past my legs ( I automatically apologised - very British). He grabbed the bag (which kind of hit me) and stalked off. He came back a min later for some nearby water bottles, and went off and found another seat (sofa squashed up with someone else's coats). He was clearly annoyed. Aibu? We are newish to the gym. Was the seat his and should I have offered it to him?