I think the key phrase is "and a third party estimator tool I used to double check the numbers" as opposed to the 1444 forms that the clients did not keep. We ask "Did your get your Stimulus Payment?" they respond "I don't remember." and we try to guess as to whether they did or not. 

I currently have a client on extension because of EIP1 - they never deposited what was likely a debit card they tossed as junk mail. I am trying to get the card reissued because their 2020 income increase and the $2,400 will evaporate.