Had the exactly same problem. Savegame was overwritten already, so any way I can't give it for evidence.
But here some facts:
0 towers in the map (same as Author)
Only the items what I left in the inventory (same as Author)
In the statistics, damage, best hit and kills with values “none” (same as Author)
Round: about 450+/500 (but less than 480)
Dificulty: Hard
Map: The first one (same as Author)
Bug occurred after exiting the game using the phone "launcher" (android), not the game menu.
This is my phone:
ASUS Zenphone 2 Laser ZE550KL
Android 5.1 (Rooted) (No "Game Hacks" used or tried.)
P.S. I'm also apologize for my english (I'm from Russia), an lots of copypaste from Magus's message.
I must say, the save game was overwritten, but I start a new game, exit in the same way (via Phone Launcher), and 0 towers, none stats, etc... etc...
I have this savegame now, but really, I want to play D: