Yes absolutely the fault of the sender, because is clearly stated in the casino terms and conditions that deposits via wrong coin network is a lost for the depositor, but in few cases we see that gambler's get lucky that the deposits with wrong network or coin as far as the coin and address is the casino valid payment details their treat is as mistakes and credits the gambler accounts with the right amount.
I quote the above case as a precidence to what really string up in my thoughts, and this question goes to those technically exposed gamblers, where do the coins actually goes to in reality?
Are coin send with wrong network actually lost?
Do casino have a system that can retrieve the money?
One thing is certain:
These funds are not completely lost.... they continue existing in the BEP20 blockchain, which is associated with the destination address. However, they are often inaccessible to the exchange system that only recognizes deposits via ERC20. Could casino recover these funds? Yes, they could do it manually, but imagine if every time someone deposited incorrectly, someone employer had to retrieve the private keys of exchange to recover the funds manually?
Besides being time consuming, it also compromises the exchange's security. Do you agree?
I believe the casino could recover this amount, but charging a high fee for the cost and risks involved, and also with a reasonable resolution time to be able to do so safely.