I need to prove I did NOT receive a check or a direct deposit .

Terry Says

There used to be a spot on the IRS website where you could track your stimulus payment. It is no longer there.
Instead you should create an IRS ID.me account, using the information in this link to a recent column.
That should show payments issued to you.

When you file your 2021 tax return next week, claim the unpaid stimulus on your return. That will trigger an investigation.