<human>: I moved into a 3 bedroom apartment in Brooklyn in September for school. 3 roommates were already there, 1 of which was leaving because one of the roommates was allergic to her dogs or something to that effect, but really I think they just didn't get along. Their loss, my gain, etc.

I didn't receive a copy of the actual lease until October, when I also received a document billed as a "transfer of rights" that would transfer the lease from the old tenant to me.

I never signed the lease transfer agreement.
I was originally under the assumption that the rooms were rented separately, but months into the thing I've found that we are all together on 1 lease.  1 of the other 2 roommates is notoriously low on funds, late on bills, etc. So the landlord consistently hounding me about the rent balance is what made me aware of the actual terms of the lease agreement.  So we've all been essentially paying 1/3 of the rent separately out of convenience.

The late-paying roommate seems to have taken his things and vanished, 2 weeks before the lease is up. He has an outstanding balance for the last couple months. I assume he won't pay because he lied about establishing some sort of payment plan with the landlord, 

So, having not signed the lease transfer agreement but essentially living as an implicit subletter for the last 9 months, will legal recourse come back to me when the landlord goes after the lease-holders for his back-rent? I understand that if it's not me, it'll go to the prior tenant, but for now I'm just trying to figure out exactly what situation I'm in. 

Thanks for reading.

Can you condense the text into a few key points?
<bot>: moved into an apartment with 2 other roomates, never signed my sublease agreement. 1 roomate hasn't paid his portion of rent, and vanished. Am I liable or is the original leasee?