What do I do?

I had a conversation with Caeden today that just broke my heart. He was sitting at the table and I was cooking, I figured it was a good time to find out how things are going for him at school.
Me: "Are you enjoying 1st grade?"
Caeden: "Yep, I like my teacher."
Me: "Who do you play with at recess?"
Caeden: "No one."
Me: "Don't you play with Josh?"
Caeden: "He likes Caleb better than me."
Me: "What about that kid named Ammon you talked about when school first started?"
Caeden: "He only plays with Alex. I just play Pokemon by myself on the playground. I don't have any friends. I wish Aaron would leave his new school and come back to be in 1st grade with me." And then he starts to cry.

And his mommy tears up herself. What do I do? Where is that elusive Perfect Mommy Handbook that has the chapter that tells me exactly how to deal with this situation? Caeden is very social, he's friendly, not shy, he always seems to be nice to everyone, he likes the same things the other boys his age do: Pokemon, Transformers, Star Wars, he doesn't smell, I send him to school in nice clothes. Why doesn't he have any friends? My heart is just aching for him. When we first moved out here he made a First Friend (his term) right away. For two years he and James played all the time. They got along great and even when James moved an hour south we still kept in touch and visited when we could. This last summer James moved to Washington. Caeden was very sad, but handled it better than I expected because he had made another First Friend in kindergarten. Aaron lived just a block away and since we carpooled with his mom he and Caeden played at each others houses 4-5 times a week. Well, as luck would have it, Aaron's family decided to move to California and he wasn't able to join Caeden in 1st grade this year.

The mommy-bear in me gets angry that the other boys in his class don't see how lonely he is and make an effort to include him. But rationally I know that kids that age just don't have that kind of empathy and they can unintentionally be cruel. Do I hope this blows over? The school year has just started he has plenty of time to make friends. Do I talk to his teacher....see if she notices anything, or has suggestions? Do I just give him lots of extra love and play time with me when he gets home and hope that it makes up for it? Or, do I just back out of the situation all together and let him handle it.....after all he needs to learn to deal with an imperfect world, right?

He's outside jumping on the trampoline right now and has already forgotten our conversation. His mommy, on the other hand, is going to be sending lots of prayers up on his behalf tonight and then she'll toss and turn half the night worrying about him.