Stimulus check for a 17-year-old on survivor's benefits

He received a letter that an EIP of $1,400 was sent to him, but he hasn't received it.

His mother received her payments via a credit card, but he has not. Is it supposed to arrive via check to his address? Would the tax return be the way for him to ask for it? If so, would he ask for it or would it be the mom (since he was 17 in 2021)? He turned 18 two months ago.  Where it TurboTax would that be done? Should he contact the IRS directly? He tried using the number of the letter [phone number removed]) but there was no way to find a human.

Thanks.