Actually he is. on the last panel, if you look near the Spidey on the left's leg, one HIS left side, you can see his mask. Plus on the way left near down the panel you can see the mask of Spider-Prime (another Spidey I think they couldn't use). On Dan Slott's twitter, he once posted "Guy way in the back (I think he meant anybody you can spot) who might be him? That's him." How about the rest of you guys? Notice any other surprise Spideys?