Please help!! Tech help for Happy Street....

So my son and daughter were both playing Happy Street on separate devices (iPad and iPhone)....but under the SAME GameCenter account. (I know, I should have had different accounts, but there were other conflicts with other games, like DragonVale, that led me to keep the same GameCenter account on both devices).

Anyway, when either of them loaded Happy Street, it gave them this message "It looks like you used to play Happy Street on a different device, do you want to load the previous data?" - with a check mark or 'x'. Each of them knew to press "x" so it wouldn't load each other's game on the wrong device. However, just a little while ago, in a fluke mishap, my daughter hit the checkmark and now my sons town is on her device and hers looks gone! This is not good.....and I hope you're following so far so that someone can give me some help!!

Is her town gone forever, or is there some way to get it back??