If you left it there for a really long time, and he gave you notice to get it, and you didn't - He can legally get rid of it if the proper channels were used.
When you say you left your truck there that you were "working on", I just picture a truck sitting in my driveway for months on end.
If this is the premise of the dispute, you will need to go to small claims court and have a judge rule whether or not "this friend" used the legal channels to implicate abandonment. Usually this means they have to send you a certified letter giving you X amount of days to pick it up. Anything short of this letter, probably will be deemed illegal.
To answer your question: On it's face, your friend's actions are criminal. The part I believe you're leaving out, is that your friend has a defense whereby he told you to get the truck on numerous occasions and you didn't, thus he sold it. If that's the case, it's a civil matter and will need to go to small claims to determine whether or not it was lawfully abandoned.