I finished the tournament D class and I collected the 150 prize gold and the 50 gold for defeating the enemy but then my app quit and the gold is gone. 
I reopened it again and still it’s not there.
Help is appreciated.
Your app crashed or you closed it?
The game is saved when you enter town, so the fact that the game’s closed straight after claiming the prizes & you didn’t go back to town - the golds weren’t saved.
This is a known common bug, admin once said it’s going to be fixed, not too sure if it’s with the next update.
For now, you’ve lost those golds & not going to get them back. Unfortunately.
Oh well I’ll earn it back in other arena matches. Thanks for the quick reply