So did some more research and I found out that I might be considered a co-tenant after all.

I lived there for a month and a half. I rented half of the first month, and paid that check to the supposed master tenant. However the last month, this december, I made out the check to the landlord which I have bank statements proving he cashed it. At that point is it not implied that I'm a co-tenant?

Sure there was a written agreement between me and another tenant that I would sublease. But it clearly states on the document its not valid if the landlord doesn't sign it. All that's left is an oral agreement which technically ended in december when I made out a check to the landlord.

There was no lease the apparent master tenant was signed too. Just a month to month verbal agreement between the tenant and the landlord. The other two roommates were never signed on any lease either so technically they were implied co-tenants as well. And because there was no lease, the apparent master tenant was still allowed to sublet to me for half of november.

If I'm legally considered a co-tenant, I can sue him for not taking the necessary steps for the abandoned property code and hold him liable for my belongings.

Can you guys think of any other ways he could argue against this?