Check your tax return. If you did claim a rebate, it will be listed on line 30 of your tax return and included in the refund calculation you were already expecting. The rebate is not a second check.
If you claimed an amount on line 30 and the IRS reduced your refund, you will need to wait for them to send a letter explaining why.
You can also check your IRS online account. If the IRS issued a round 1 or round 2 payment to you, they would remove it from your tax return. If you never received the round 1 or round 2 payment, but the IRS thinks they issued a payment, you will need to initiate a Trace of the payments.
https://www.irs.gov/coronavirus/get-my-payment#first-second-payments
