I think you were wrong to make a game out of it. But if one of my friends said they were just heading to the bathroom and they weren't back after 20 minutes i'd be going to check on them, never mind two hours. I would be genuinely worried and wanting to know if they were ok. Opinion seems to be that you are making too much of it but if i was sitting watching a film with a friend and they just vanished i wouldn't be able to just sit there and forget them and enjoy the film. I would have to check for my own peace of mind, the fact they didn't does to me demonstrate a certain amount of thoughtlessness. How you tell them without making a big issue out of it i don't really know.