I need help. I was battling with friends at Big Ben Tower when I reached the top where Meowiarty is. Close to the end, I get defeated. I flee and regain health and mana, teleported back to my friends but they had finished it. So, I went back to the museum and went back to big ben. Suprisingly, there were no enemies. However, when I went back to the top, Meowiarty wasn't there. What should I do?
When you enter a dungeon (or tower, in this case) via the glowing sigils, a special version of the dungeon (called an "instance") is created just for you and your party. That is why you don't see anyone else that might also have entered the dungeon right before you.
We know that sometimes, despite your best wizardly casting, you may lose a fight. So, the dungeon remembers who enters the dungeon. If you exit the dungeon to go heal, you can usually get back in without resetting the dungeon - but only for a limited time. Even if everyone in your group exits the dungeon, it may still remember you were in it and stay around in case you want back in. That's why there were no enemies when you went back into Big Ben, because it was still the same version and was just waiting around in case you came back.
Dungeon memories vary. Some can be less than a second while others can be up to an hour or less. After that, it will act like you have never been there before.
Unfortunately, since your fellow students finished Meowiarty while you were gone, you didn't get credit and will have to do (just) the Big Ben tower over.
By the way, this dungeon "memory" is also why - sometimes - the dungeon tells people it is full even though some of the students in the dungeon have left it. It is 'saving' a spot for them, in case they want to come back.