The problem is and what has been explained is apparently when the landlord deposited the check it didn't end up where it was intended to go and into an account that is not the landlords.
This is a possible bank error. Since the account is not the landlords and they have no way to prove that the landlord 'owned' the check, they will go back to the check writer.
That can start the investigation rolling. The bank will contact the depositor and ask them to verify why they deposited a check meant for another individual.
If that individual now claims the landlord endorsed it to them, it opens up dialogue between the bank, landlord and the depositor.
if that individual comes back and simply says he doesn't know why he got the money, they reverse it and deposit into the landlords account.
Either way the OP has to be involved a SMALL part to start this.
It's insane people think otherwise.
Unless I missed something, the landlord openly admits that he received the check, there is nothing to "prove" in that regard.
TJ presented a valid method of payment to LL...and...that's the end of TJ's liability.
-You buy a motherboard from me.
-You send me a check, and I send you the motherboard.
-I say, "Dude, never got your check".
-You look at your account, and the check has been posted as paid. You tell me this.
-I say, "Well okay, I *did* get your check...and wrote my account info on the back, but didn't deposit it, so, someone else must have cashed it. You should send me another check bro."
-This is when you tell me to go piss up a rope, and rightfully so.
What am I going to come after you for? What "small claim" do I have against you?
TJ actually took a couple of steps above and beyond what was required in an (apparently futile) attempt to diffuse the situation.
LL is shady, with a capital "Asshole".