What a disturbing news, Ram. More than the loss of the materials, it is the belief of your friend and his GF that has been betrayed. It takes a long time to recover from this.
I had a similar but much less dangerous thing happen to me when I was finishing up my grad school and was moving from one foreign continent to the other - I had an enormous quantity of books and notes that I didn't have the resources for at the time to move to my new place of work. A 'friend' who had a house volunteered to keep these 30 boxes of books etc in his basement and ship to me later at a date convenient to me. I'd pay him of course. In a few months time when I wanted the books shipped, the guy could not remember anything about my boxes. When I pressed hard, he said something about some flooding in the basement and he said perhaps all my boxes had been thrown out. Till this day, I cannot forget this. Till this day I have a hard time coming to terms with what happened. Since then I have bought many of the books back, but cannot replace the enormous volumes of notes, homeworks etc that I still need from time to time.
In this case, why can't something be done about it. I understand both your friend and the offender belong to some other forum. Can't the offender be traced using this other forum? This offender should be brought to justice, it's a criminal offence.
Regards.