If it were me .... ME .... I would have, in the middle of the night, slashed his tires... cuase I'm one outrageous person...
OR, in a calm sence, I would have gone to his apartment, calmly, and explained to him, no one, who lives in the apartment complex, enjoys listening to his music that plays way to loud. Then I would have confronted him by saying, " if you took my bike, then I suggest you tell me now before I find out later and then really be stirred up.", then of course, in response to that, I'm sure he would say something like, " i never took your bike you $%#%!" and then I would have said, " yes you did. You took my bike becuase I filed a complaint about how loud your music is. Your music is so loud, it's ridiculous. And why do you play it so loud? No one knows, maybe it's just cuase you want it to be loud so everyone can here. You want it to be loud becuase you want everyone else in the building to hear your great music, and then in return, by playing it so loud, you would feel a sence of great accomplishment, knowing that everyone in the building has heard the great wrath of your music, and that gets you off and makes you feel superior.. who knows... I'm just saying. Now please, turn down your damn music, or turn it off before I have the police over here, telling you the same words I am now. Oh yes, I can I tell them you stole my bike, considering the circumstances, you seem like the most likely candidate to do it, so how 'bout it?"
Then, I'm sure, he would either 1, be wordless, 2, be super mad and slam the door, or, 3, yell and cuss and cuase a horrible mess. If he did choice three, I would have gone back to my apartment and called the police.
Anywayyy.... That's what I would do ... and if the situation gets worse ... consider moving out maybe.
Hope this helps! :]