Depends who’s asking you for the money back. Is it the casino asking for the money back, or is it the poor fecker who accidentally allowed this to happen and has had to pay the 1500 back out of his shite wages? I worked in a betting shop and if my till was down it came out of my pocket, particularly if I wanted to keep my job. I’ve no idea how works on the online betting industry, but I should imagine it’s not too far away from the betting shop methods… poorly paid and poorly trained staff living with the threat of losing their job at any moment because of one lapse of concentration over the thousands of transactions that take place… I’d pay them back in a heartbeat.
If it’s the actual casino asking for it back, the one that would sack the above worker, then feck ’em! Trouble is, it’s not easy to tell who you’re dealing with without asking some probing questions. You probably did the right thing though and possibly saved someone their job.