About Spidey's whereabouts during Avengers 1...
I really don't think it's such a huge issue. There are any number of things he could have been doing, such as:
- Kidnapped by a villain (The Jackal's MO, but take your pick)
- Fighting a villain underground, in a far off part of the city (would have been completely oblivious until after the fact)
- Could've been in an area so densely occupied that it would've been impossible to leave without giving up his identity (Hell, he could've been among the people Cap saved from the Chitauri)
- Could've been in the hospital with a severe injury (or refusing to leave the bedside of a loved one in that situation)
I'll just be enjoying the ride.