I've never read such a fanfic, but I did once have an idea of writing a long fic where Wilson is in some kind of an accident and when he regains consciousness, he has lost the last three years worth of memory. So, he doesn't remember starting a relationship with House, nor does he even know that he's gay now. (This admission/realisation comes much later.) As far as he's concerned Amber is till alive and they're dating. So he has to go through the whole grieving process again and he doesn't feel as though he can be in a relationship with House again, and poor House has to try to make him fall in love with him all over again. Someone once did an excellent job with this in a Goren/Eames Criminal Intent fanfic.

Which, of course, has nothing to do with House losing his memory. This would be a very intriguing idea...maybe you could try it?