Hacking of characters is extremely rare and even then only tends to happen to people with easy passwords, which Markus does not have. However, he could have been hacked. If he has been, then obviously, his losses will be restored.
For the record, and for the genuine Markus if that is the case, the following seems to have happened: Markus was slain by Marie in Parrius. He waited around as a ghost while Marie cast spells on him, and after about five minutes was forced to perform a SUMMON SHIP act by Aragorn. At this stage, I was told that he had lost around three levels. Then, once on the shore of death, he did not receive any message informing him to BOARD SHIP, and therefore he stayed there not knowing what to do - hence the BB messages, etc. During that time he lost a further few levels until he was finally resurrected.
I restored all but two and a half levels of his loss (since he had lost some by being slain and by waiting around as a ghost), believing his reason that there was no BOARD SHIP message so he did not know what to do. This, as far as I know, was all the real Markus.