What a bummer! Have you considered that the gold may have been exposed to chlorine, either in bleach or chlorinated pool water?
I once had a 14K gold ring that fell apart while I was at a
health club. Not knowing anything about metals at the time, I
assumed that it had something to do with heat in the sauna.
Bleach, Chlorine? That may have caused the problem . . .
Wondering how many times would gold have to be exposed to these
elements before there would be a problem?