Assuming that you were not being claimed as a dependent on a 2021 or 2020 tax return -
On your 2021 tax return you were asked if you received the Economic Impact Payment (EIP3). If you indicated on the tax return that you did NOT receive the payment then a Recovery Rebate Credit of $1,400 would have been entered on your 2021 federal tax return, Form 1040 on Line 30.
If the IRS has records showing that they sent you the EIP3 then the IRS would have removed the Recovery Rebate Credit from the return you filed.
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 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...
The EIP1 of $1,200 and EIP2 of $600 would have been sent to you by the IRS during calendar year 2020.
Go to this IRS website for your tax account to see if EIP1 and EIP2 stimulus payments are entered - https://www.irs.gov/payments/your-online-account
