Hello, I'll try to describe the problem.
1) Authorization CustomID + CreateAccountN1
... play game with CustomID + AccountN1
2) Facebook Authorization + CreateAccountN2 + LinkCustomID. After that, CustomID loses its AccountN1.
... play game with CustomID + AccountN2
3) Then I go out of Facebook and run UnlinkCustomID.
The question is how can the CustomID return to its AccountN1?