hmmmm....
He remembered Obi Wan
R2 remembered Obi-Wan... and Obi-Wan should have remembered the droids. That is a plot hole. But they made a point of wiping C3PO, but not R2D2.
No, he didn’t. R2-D2 is the one who said he belonged to Ben Kenobi. C-3PO said he had no idea who that was or what R2-D2 was talking about.