Thank you for all the hugs and the sympathy. A mutual friend talked to him a few days ago (and found out that he has a severe concussion), and they've agreed to meet in the next few weeks to exchange our things.
This friend is outraged at the way he's treated me, and told me she honestly did not believe him capable of such cowardice or cruelty, so she was blind-sided too. She has agreed to ask the one thing I think I really need to know: whether he left because he had fallen in love with someone else. I know the truth will hurt, but if it was that he had fallen out of love with me and for someone else, then I can salvage some of the good memories. He will still be a horrible coward for not telling me he didn't love me anymore, but it won't cast such a pall over the last five years. Or if she's just free rebound sex, then it will confirm his immaturity. She has said if he asks about me at all, she's going to say I'm handling it remarkably well, and then unload on him everything she wants to say about the matter. Actually, she said she might unload on him either way, once she has my things. I'm not going to ask her not to, because I want him to know that he has lost friends by his behavior. If he had just been honest, we could've been friends in the future, but instead he had me coming by every week and making him dinner, then cut off all contact with me after promising to meet and talk.