IRS has lost my 2020 paper return but cashed the check that was mailed with it.

IRS has lost my 2020 paper return but cashed the check that was mailed with it. I did not find this out until after I mailed the 2021 return.  I called them and after 2 hours on hold the agent on a really poor connection said the return "was there" but said I should send another copy of the 2020 return to a PO box 8208 Philadelphia PA 19108. Now I am worried whether or not this address is correct. Meanwhile, the IRS website transcript function says no tax return filed even though the payment update says "Payment with return". Does anyone know if this is correct address?