I'm a mom, and I've got your back. I'm amazed at the difference between the freedom I experienced as a kid in the 70s and the short leash my son's generation enjoys. Granted, I was freaked out the first time he took the bus alone and the first time he flew to California by himself I close to polished off a bottle of Makers' but that's my problem, not his.
My one question is regarding the cell phone. If my kid wasn't responsible enough to hold on to a cell phone, I would question his ability to negotiate the rest of the trip. Was losing the phone really an issue, or did you want him to manage the trip without the security blanket of a quick call home?