That doesn't mean its wrong.

Anyone who abandons a Bianchi for 2 years A) probably didn't care about the bike when they left it there, B) sure as heck don't care about it now, C) are careless and negligent, and D) don't deserve that bike anyway. Other than how it may be considered legally, principally I don't think its any different from taking a thrown-out bike out of a dumpster.