Hi,
Mods probably won't do anything as you didn't catch it so they can't know its IDs and therefore respawn it
However, there is a boss in Unknown Place (Trainers Valley) which should (never had to deal with him so I can't tell for sure if it's working or not, but it should ^^) give you another opportunity to catch Mew -if you defeat him, of course-.
Now, regarding this freeze, was it when you opened your backpack in battle? Or random freeze?
Given that Mew is still awake and full HP, I'll assume it was random; my best guess is that the server timed out, and there's nothing you can do about that;
But if it was indeed the backpack-thing, from now on, open your bag in battle every ~20min (the longer you wait between 2 openings, the longer the game will freeze)
Anyway, it's sad, but things like that happens :l
Hopefully, you'll manage to defeat Nikola and get the second Mew :p
It was the backpack glitch, but how am I suppose to catch the Mew without opening my backpack and throwing pokeballs at it? Wait 20 mins inbetween every ball? This wasn't a mistake on my part