I've upgraded my tower twice now, and both times it's gone back to the previous tower, but my fairy dust is still gone. I'm out 10,000 now. I play on both my tablet and Facebook, if switching back and forth might be part of the issue.
I've just sent you a message which you can find by clicking on the mail icon in the top right of the main King Care page if on PC, or tapping the left hand menu if on mobile/tablet.