It's very frustrating when anyone talks about sexual assault and people go all "well if you report it it will go away"

Yes, you should always report an assault, even if nothing gets done it puts the record out there. However, that's just it! Sometimes nothing gets done. When they don't have any hard evidence and no witnesses come forward, it's very difficult for anything to be done.

But for a moment I would like to talk about conventions.
I've been creeped on at cons before. People like to pretend that doesn't happen, or that all women/girls are making it up or exaggerating the facts.

Looking at this from a predators perspective, conventions are great places to hunt for victims. You have tons of vulernable people to choose from, even children whose parents have dumped them off at the con while they go enjoy a latte across the street. This is a place where people believe they are safe, after all they are surrounded by people like them. Sure there's lots of people around, but how often do you know what's going on around you with that many people around? People are looking at the tables, at the cosplayers (and booth babes if they are there), they are not going to notice some creep leading a young girl away (who is probably too terrified to scream).

My advice to anyone at conventions.
See something, say something! Security might not always take the report seriously, but believe me if you make a big enough stink about it they will have to do something (just don't get yourself thrown out). And if security doesn't do anything, make sure other people are aware of what's going on.
Same for if someone tries to assault you. Say something, let the world know you said "NO!".
Don't believe the line, "my buddies are up in my room. " Maybe they are, or maybe there are no buddies. Rapists have used lines like this before to make their victim follow them to a secluded place.

Be aware of what's going on. And STOP PRETENDING IT DOESN'T HAPPEN!!!