This is probably the lamest thing to comment on, but the comic book...

I'd imagine the turn-around time for a comic is quite sometime. The prints Issac turned in were in black and white, so they'd have to get colored and have the text written and get published and sent out. I'd imagine it would easily be possible for Issac's work to still be issued for several months after his death.

I honestly have no idea, but it seems possible.