Genuine AIBU here. Just got on a train to find a couple sitting in the seat I had booked and the one next to it. Didn't realise they were together at first so said to the lady in my seat "I'm sorry, I have that seat booked'. (Just for info, in ROI. Your name is on an electronic display over the seat. You can book a flexible ticket which lets you get on the train before or after the one you purchase the ticket for, but if you have reserved a seat, it's obviously only valid for the train you originally booked).
Anyway, the guy spoke up and said they had also booked the seats, and showed me their tickets as proof. After a moment's confusion, I spotted that their tickets were for the later train. They said they thought they could have those seats on whichever train they booked, but when I explained the situation they accepted it with good grace and moved.
Two more pieces of relevant info:
- There were other empty seats on the train so I could have sat elsewhere but it probably would have taken a while to find one that wasn't reserved.
- The man's seat was also reserved, from the next stop, so this may have arisen even if I wasn't the one to tell them.
Was I a cow? Why am I embarrassed?