I'm not sure many people in this thread read the entire OP...
Sounds like OP is trying really hard to justify taking someone's stuff without even a good faith effort to resolve the problem. Lots of good advice so far, which OP just dismisses while salivating over a bike.
He didn't contact the LAPD, and that is probably a failing. But I'm not sure he even knows the missing roommate's name.
So you signed a lease with a person that you know nothing about?
Have you never been through this process in college? I haven't but at least I know it. In college areas, it is very common for someone to sign a lease in a multi-room apartment directly with the landlord, and not know who the other roommates are. Hell, even when moving into a college dorm, you may have no idea who your roommate will be. I knew a guy in college who lived in a house with seven other guys. He didn't know them beforehand.
The OP also noted that he took a tour of the apartment with the landlord and never met the other roommate at the time.
The landlord is the one with the responsibility to deal with the stuff left behind, and is the only one with a right to the stuff. If there's an issue, take it up with him.
The OP stated on several occasions that he did try to contact not only the roommate, but the landlord, and the lease holder. As far as that side of the story goes, how much more can he do? If they don't even have contact info for him, then what?
Seriously, it's like people didn't read anything the OP wrote outside of "I really want his bike". You saw that and your nostrils flared up and everything else became irrelevant.
When these friends of his showed up asking to see his stuff you should have told them to leave and come back with the roommate.
Ummm...he said pretty much exactly that....
This is an interesting conundrum. If the landlord does nothing and the lease holder does nothing, how long should the other roommates put up with this guy's stuff being there? Especially if there is a fourth roommate taking his place. If the landlord and lease holder rented out to a fourth person, then they are accepting that the previous person is not coming back. Indeed, they SHOULD be dealing with his stuff, but they aren't.
So, if the landlord and lease holder are not taking any action, what SHOULD the roommates do? They should not have to pay for a storage unit for this other guy's stuff.
Also, OP...you shouldn't have paid his portion of the rent unless the agreement is for the full rent, and not rent-by-person.
If you want to push the landlord into taking some action, tell him that you're going to put the stuff in storage, and take the money spent on the storage unit off your rent until he takes it over or gets rid of it.
This is probably the best advice I have seen on this thread so far. If the landlord is not doing anything about it, make it monetarily inconvenient for him. That will surely shape him up real fast. The onus should not be on the other three to pay for this guy's belongings.
Look. Three points occur.
The first is is matter of time...that same time could well have been expended in going to the college authorities and letting them know that this guy has apparently vanished.
Secondly, the title of your thread - and the tone of your original post (and several subsequent posts) give the lie to your statement in this particular post "this isn't about his possessions...." when the whole thread, from title, to original post, to much of the subsequent discussion was about little else.
Thirdly, while still posting, you have done nothing to alert the relevant authorities to the situation.
Points one and three are the same. So only two points occur.