So is mine, but it's a pretty big difference, eh? :P

Verbal agreements aside (which _may_ save your ass, talk to a lawyer) it seems to me you knowingly assigned the IP rights to someone else's code to your employer. IANAL, but I'd think any agreement you signed with them would override any supposed verbal agreement in a "he said, she said" situation. You may just find yourself in deep doo-doo. :(

Whatever you do, though, at least consult with a lawyer.