Becky talked about this before
"Going into debt
This happens when you play on multiple browsers/devices and buy stuff from the shop in one instance of the game and other stuff in a second instance. Basically, the game is combining how much money you spent in both and subtracts that from your total money. I ended up in the negative hundreds yesterday testing this out....just now getting out of debt #tooreal
This may also mess with your inventory. It looks like I only kept the items I bought second, and none of the ones I bought first. If you see wonky stuff going on with the items you own, it may be because of this. Just make sure you've closed the game on your PC before playing it on mobile and vice versa to prevent any of this weirdness. Again, this be an issue we're lookin' into it."