If it's the glitch on their own site, your proof isn't that strong to say their site is a scam.
I,myself mistakenly send out xrp without destination tag (though not in bitsler but in other gambling site) but it will just take some days but surely you'llg gonna receive your 150 xrp as long as you've entered the correct xrp address.

What I did before, I've contacted the support of receiving xrp wallet and tell them about the sent out xrp address from that site. They will get some infos or probably screenshots from you like transaction hash or something. If the transaction was successfully sent out. It's just destination tag that wasn't put in the required field. But you'll receive it in a few days.