If tenants left refuse to return keys, holes in the walls and ceiling, paint ceiling black, left pile garbage and stuff mark poison, no forwarding address, how can you sue. The court says you have to sue in distric, but if you have no idea where the person is where can you file? One is a military sergeant

You have to find the tenants by any means available to you - and that includes a licensed private investigator to locate them.

This is a prime example of being very choosy who you rent your apartment to. Did you have the prospective tenant fill out any kind of prescreening info such as former residences, landlords, blood relatives addresses, personal references, employers, and actually call up these people?

Anytime you rent to anyone in the military beware that locating anyone in the military is now practically impossible since 9-11 and is getting worse.

At this point you should cut your loses and consider this a very expensive lesson on just who not to rent to in the future.