There is no need to amend your tax return since the IRS removed the credit from your original return thereby reducing your federal tax refund or increasing the amount of taxes owed.
If you never received the stimulus payment but the IRS sent it then you need to have the IRS start a trace on the payment you did not receive.
Go to this IRS website for how to start a trace on the payment - https://www.irs.gov/newsroom/questions-and-answers-about-the-first-economic-impact-payment-topic-f-p...
