you'll never get an acceptance notification or any other kind of notification that the IRS received your "MAILED" return. in the future if you mail a return, you should use a tracking method. if the 2020 return got lost in the mail, you have forfeited your refund because the return had to be received by the IRS by 4/15/2024 unless it was properly extended to 10/15/2021
the IRS may have gotten it but it would be sitting in an unopened mail bag waiting to be processed. calling will do no good
