Did you report that you did not receive the 3rd stimulus payment and the IRS removed that amount from your tax return? If so, the IRS has records which show that the 3rd stimulus payment was sent to you.
The Recovery Rebate Credit would have been entered on your Form 1040 Line 30.
Go to this IRS website for your tax account to see if the 3rd stimulus payment is entered - https://www.irs.gov/payments/your-online-account
If you are Married Filing Jointly also check your spouse's tax account.
If you checked your bank account in the March - May 2021 timeframe and there is not a $1,400 EIP3 payment from the IRS then go to this IRS website for how to start a trace on the payment - https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-p...
