God can't "forget" anything because He has total and complete knowledge of everything.
We may see this as a contradiction, but I don't think God sees it that way.
All men are fallen and all men's sins were known to God from before time.
But through His gracious gift of salvation, God still has chosen His elect to spend eternity with Him, all the while knowing every sin each one has ever committed or will commit.
He doesn't forget our sins; He forgives them.
You're right, Seven_O. If He needed any prompting, God could always check the Bible to remind Him who's who. 8~)