What makes this even better is that refreshing the game got me all my stats back. Would playing a match have overwritten my save file and I'd be under the illusion I lost everything?
If anyone else loads up the game and is back to level 1, try not touching anything and just refresh the page. + this if it worked. Maybe playing actually makes you lose everything.
I killed over 11 thousand zombies today, got to level 15 or so. I paused the game and lost my internet connection, then I got it back and closed the tab and decided to come back for some good zombie rampage. Sure enough, I'm level one again. I guess I must've killed all those zombies without gaining any XP or using any weapon other than the free M1 Garand and the starter pistol.
 "SAS: Zombie Assault 3"){kind=icon}