Here's another one... Got it from another forum.
Spoiler!!! Click to Read!:
While Tony Stark is thought to be dead, after the attack on his mansion, he commandeers a television news van while laying low to research his attacker. After he instructs his "biggest fan" to increase the power on the roof of the truck, Stark is seen looking up information on Extremis.
In the background, one of the monitors shows that a thunderstorm is on the East Coast. What Avenger is associated with thunder? A God of Thunder.
ie....Thor 2 could be taking place in the same timeline as IM3. So that explains why thor doesn't help stark.