moldy wine cork

I took a bottle of wine to my brothers to share and when he went to open it, he found mold under the foil and on top of the cork. Eeeewwww. I saved the bottle hoping to take it back. It was a lovely french Chardonnay labeled with Michel Richard's name (BOURGOGNE BLANC, Michel Richard, Domaine Borgeot, Burgundy, France 2005)- he uses this as his house chardonnay. I called the wine store to ask and they said it happens often and that there is no problem. :) :) tg! They said that sometimes a bit of wine becomes trapped under the foil and will grow mold on the cork. I've never seen this before and hope I never do again but I am so glad to know that my wine is ok.