In one instance,
Your friend could have been able to archive this out of the relationship he must have created with the staff. Perhaps in a bid to save time and continue gambling, he goes ahead to place bets and the staff might allow it out of the trust on past ordeals with them and this time, he eventually doesn’t have the money to balance up his excess.
Of course a casino that allows for such and it must be a physical casino would have a means to getting their money back but, it’s first and foremost on the staff to have allowed such privileges.
In the second instance,
It could mean that your friend only loaned money from some place else to gamble and lost them all. Hence, without going in detail, he just ties the debt he owes to gambling. Thats messed up and a don’t do!