Money disappears

My money (the green bills) "magically" disappears if I stay away from the game for some time. At a certain point, I had 6 bills, closed the game and, when I returned, I had only 4 bills. How is that possible? Its annoying and unfair since I had purchased a few bills. Now theyre lost. Im really upset.

Mmca95 about Cooking Academy - Restaurant Royale, v1.18