"He did not receive a W2-G gambling form or 1099."

That's because it's a Game, not a casino. You're not betting real money.

"Since Chumba Casino operates with play-for-fun currencies and it’s considered to be a social gaming platform, we must say that the whole payment system is different compared to the one you can find at other PA online casinos. Gold Coins or Sweep cash aren’t considered to be real money."

"Don’t let the word Casino mislead you. As we've mentioned in our review, Chumba Casino isn’t an online casino in the traditional sense of the word. It’s conceived as a social gaming platform offering the possibility to play casino games, but it’s not casino since it doesn’t involve real money.

This online casino works with virtual currencies, Gold Coins, and Sweeps cash. You can only buy Gold Coins. On the other hand, you can only withdraw Sweeps cash. Therefore, playing Chumba Casino games isn’t considered to be a gambling activity."

https://www.vegasinsider.com/casinos/chumba/

That is not a loss, then. It's the cost of playing games.

https://www.strafe.com/esports-betting/reviews/chumba-casino/taxes/

"Since Sweeps Coins possess monetary value by redemption, they are classified as casino prizes."

"There are two primary ways to report Chumba taxes. The first is allowing the casino to pay withholding taxes on your behalf. You'll then get a Chumba Casino tax form or Form W-2G, which you can submit alongside your income tax returns.

Secondly, players can file the taxes personally with the IRS at the stipulated rate. In the case where you receive gift cards rather than cash prizes, you should report its fair market value as income. Gambling prizes should be recorded on your tax return as "other income." "

Which leads to me to think the $50k is casino money, not real money.

"Winnings were sent a direct deposit to his bank account"

Redemption by a US person would be the real money as a Prize.

"Legal for cash prizes to USA and Canada"

https://www.beatthefish.com/chumba-casino-review/