I realized that part after I posted it but in the case of the keep he still wouldnt be a fence. He would have bought it from a fence.
I am not naming names but this is how I see this scenario playing out.
1. The first person who is naive and possibly stupid person shares account information with a second person.
2. The second person steals the first persons keep.
3. A third person, possibly from a zerg guild, offers to buy the stolen keep.
You can reverse 2 and 3.
So, no, he bought it from a thief.
A thief steals and sells/trades.
A fence buys and sells/trades.
If you simply receive stolen goods your at the same time a moron and a creap. A moron because at any moment the stolen goods could be confiscated and you could be implicated in the crime and a creap because you knew the goods belonged to someone else and you bought them anyhow.