In every lab I've been in there are always one or two pieces of equipment that don't belong there (don't belong to the organization) but have either been abandoned by the customer because it was too expensive to repair or in at least one case ended up there somehow and could not be returned because the company went out of business.
You can't use this stuff and can't throw it away.
What do you do with it?
Own it and put it to work if it's useful. You should contact oem and see if they know of a place to check for stolen stuff.
I agree with Bryan. If equipment is abandoned, I say take it over. If I ran a cal company, I'd put in an "Abandoned Equipment Clause"
Several Reasons for abandoned equipment, failure to settle bills, project closed etc.
On failure to pay, send a legal letter demanding payment per original terms or the contract is canceled (you did put in the contract what happens if the client fails to pay, remedies and penalties... seizure of equipment, liens etc.. )
Once this is done pull it into the lab if useful otherwise give it to a HAM in your lab as it is probably something only usable to a HAM.
Aloha