Granted the details of the situation are a little bit different, but a couple years ago, I found a huge Nishiki Marina out at the curb. It looked abandoned, as it had flat tires and had been sitting there all day long. I knocked on the door of the house, but nobody was home. I came back for it later with a paper and pen. There was still nobody home, so I picked up the bike and left a note. I gave my phone number and explained that the bike looked like it had been abandoned, and that if it wasn't, I'd be happy to return it in the exact condition that it was in. A couple days went by, and I was beginning to think the owner had completely moved out or something. Then, someone called, and told me that the bike was abandoned, and that I was welcome to it. Conscience cleared, I disassembled it and sold off the frame.

If it really means that much to you, I'd try to find the fellow's name, and send him a letter explaining that his bike is being ravaged, and that you're interested in saving it. Offer him the choice of you holding onto it until he wants it back, or buying it from him. Mail him the letter, and enclose a self addressed, stamped letter so he can reply to you. If you ever get a reply from him giving permission to save it, I'd say you're in the clear. Granted, he might never respond, or he may say, yes, save it and hold onto it for me, but you'll be in the right if you go about it that way.

Don't expect to visit this person in jail. Unless you're clergy, or close family, it can be a huge hassle to get permission. You'll already be in the midst of one major hassle, so why not make the rest easier and rely on the U.S. Postal Service?

Good luck.