sorry you and Coley had a rough time. Maybe he just feels comftrable 'letting go' around you, because your his mother? It seems like maybe he was having a hard time while he was there, maybe just holding it together, but it was probably building the whole time, and when he seen you he might have figured if he convinced you he could go that you would take him home, and he wouldnt have to endure it anymore.
Reminds me of when you said about the baseball team and him running away. It is just really rough on a person with aspergers/autism to be around a group of people you are not comftrable around, I know I described it, sort of like your 'flight or fight' response is always on and you want to run to get away from the group of people, but it seems like he knows that isnt aceptable to do, so he stays with the group and fights back those feelings. It seems like he probably had all he could take of that and when he seen you he let loose, and the 'flight' part kicked in thinking you would just take him home.

I can relate to situations like that, but everyone is different. When I was a kid I did stuff like that all the time, and I am not sure how my mom survived it, but she did (she just dyes her hair to get out all the gray )