Sounds like he mistook your "go-back" wave for a "go-ahead" wave.
I know people telling you to be more careful gets old pretty quickly, but it's best to assume that the average driver really isn't going to be doing everything they can to ensure the safety of cyclists, and to act accordingly.
Sounds most like this, although I imagine I looked insane when waving...
Sounds most like this, although I imagine I looked insane when waving...