I told my friend about your situation, he totally understood.
He suggested that he will leave for Siem Reap with his family for 4~5days from Phnom Penh, and he will still leave the cash to the safe keeper at the hotel reception, just in case you found someone who can trust to get the money.
He will let me know the room number, and envelope addressed to Mr. Lewis Martin or the name from the bank account.
He will buy a local cell card from airport or from the hotel service, so you could call to let him know after you received the money.
He said that he will stay in the same hotel before they leave for Vietnam the next day.
He said that's the best he can do to help me.
I am so helpless, I really don't know what to do now, so I let him decide what he can do.