Update following Mike's comment
===========================
Mike, thanks for contacting me.
This is a very simple story: I won an auction on eBay several years ago from Heroes, at the time if I remember correctly they were located in San Jose before moving to Campbell.
I visited the store and ended up buying other pieces on top of the Kirby I won - a couple of Byrne pages, a Mignola pin-up, an Art Adams piece... and this sketch.
I just thought the sketch was nice and indeed, it reminded me strongly of the Neal Adams drawing but I was not familiar with your work and thought, maybe you did lightbox for some sketches, or did a couple of drawing very similar...
I did not think of questioning the seller since I probably spent 3-4K for all the pieces (a bargain compared to prices of today ;-) and the sketch was 100 dollars or so.
The store owner seemed also quite knowledgeable and had several Neal Adams pieces so I did not think of asking many questions...
I just sent an email to Heroes and copied you Mike. Hopefully they can explain.
If you want, I can remove the piece and close the gallery. I do not mind at all.
Now... honestly, the other reason I did not think too much about the signature was that if somebody wanted to fake something, he would have signed as Neal Adams don't you think? Less suspicion, easier to sell...
But I agree - the pose, style, quite weird. Maybe an interesting story after all behind this piece? Who knows... Let's hope we learn more very soon!