Could he have met the “mystery woman” online before he moved there and gone to Bulgaria to be with her?
Could be. Also, who is to say this was a genuine love interest on her part and not a scam of some sorts, having met him either online or in real person.
Perhaps it wasn't an accident, and her boyfriend or husband found out?
Maybe after he reappeared after his hospital visit, perhaps this time he was 'disappeared'...?
Did James ever communicate the name of the women to anyone...family? Friends?
Also, surely Vlasta Hospital should have his name. He may have been unconscious when he got there, but he obviously regained conscioussness and felt well enough to discharge himself later on.
Also, why did he discharge himself? What was the big rush to leave hospital?