I'm not saying that convention relationships do not work, I know a few people who met at cons and started a relationship that is actually working! This is just my experience that I want to get out of my chest.
It was over a year ago in a small convention when I met this guy. The con lasted three days (Friday-Sunday). I just got to the con area, changed to my cosplay and sat down and had a snack after a long bus trip. This guy, let's call him F (for fuckboy) and his friends joined me out of nowhere, I knew none of these people, but we had weird and funny conversations. I did not take a notice on F in the group (there were 3 guys), but after that weird chat, F came up to me many times during the first day of the con (he was actually one of the workers in the con, so he basically tried his best to find me when ever he had breaks). When it was late (read: close to midnight), he asked me to join him for a while in the evening, since he had to check on peoples con bands alone. I stayed with him for a while, but soon left since, well I really wanted to sleep.
Now on Saturday F started to show more interest in me. I assumed the whole day that he was just joking around, that's naturally how I think/react when this kind of shit happens. Well, it was evening, I changed out of my cosplay and just hang around with my group that I arrived to the con with. It didn't take long until F joined us, and asked me to go outside for smoking with him a few times. When we smoked our last cigs for the evening, there was only one seat left, and this is where he suggested me to sit on his lap, ok, cool, why not. I sat on his lap, he licked my face, and kissed me and made it clear to me that he was really interested, after that evening, he called me his girlfriend, and tbh, I didn't mind. Sure I didn't know this guy that well, but hey, I wanted to believe that this would go somewhere. I mean, he seemed like a nice laid-back guy. And sure, he was. I admit.
Sunday was the last day of the con, and I spent almost the whole day with F. A friend of ours kinda saw this happen and announced to a group of people (her friends I assume) that F has a new gf. The group of people asked who, and she pointed at me. People, gave me quite nasty looks and probably at this point bells should've started ringing, but no, I did not think about it much at the time, sure it was uncomfortable to be stared at, but I shrugged it off. I mean, during the whole weekend, this guy was such a gentleman for me and we shared same interests in gaming and music.
After I got home, he took contact almost immediately. We talked everyday. We both also had cars, so visiting wasn't a problem. His text patterns sure were fuckboy-ish most of the time, but I let it slide.