Another Blade Runner blooper?

I was watching Blade Runner last night and observed a weird thing on the side of Roy Batty while he was in the phone booth having a little "turn" at the beginning of the movie.

Who's thumb is this?

I've literally never seen it before, despite the number of times I've seen the movie.

I can only think it was edited in (this is the theatrical release) because they didn't have an appropriate "Joiner" between him being in there and the rap at the glass from Leon outside...

I can't find any other reference to it on the net