This is the relevant reference from the Books where Possession is mentioned.
I make no pronouncements on these matters, but report them as I find them.
Arrive at your own conclusions.
I wish you well,
"I was her master," I said. "It has been a long time. By now she may have fallen to another. Lapses have occurred. Who knows what collar is now on her neck. She may be a camp slave, a paga girl, a field slave, a caged brothel slut. Others may now have as much claim on her as I." Possession, particularly after a lengthy interval, is often regarded as decisive, by praetors, archons, magistrates, scribes of the law, and such. What is of most importance to the law is not so much that a particular individual owns a slave as that she is owned by someone, that she is absolutely and perfectly owned. It is the same with a kaiila, a verr, a tarsk, and such.
Swordsmen of Gor Book 29 Page 452