-snip-
Either way, he should contact the support and they might be able to send it back to the source address if it wasn't already spent.
I agree, the only way to get a solution here is to contact the support. The support email address was
support@freebitco.in when I had a problem long time ago, but I don't know if it is still active and being processed. Otherwise I am sure @TheQuin can help you, too, if you write a PM to him.
In general:
I hope that a withdrawal address of player A will not be used as deposit address of player B ... Freebitco.in has control over the addresses, so it should be possible to track the transactions and refund the coins if necessary.