If you and your GF live together then only one of you should claim your child. If GF claimed your child then you should not have entered anything about the child on your own tax return. Did you use the recovery rebate credit on your 2020 return to try to get the $600 stimulus check?
There is a number to call the IRS for lost or damaged refund checks---try that number and see what they say about your lost stimulus check:
https://ttlc.intuit.com/community/refunds/help/how-do-i-replace-a-lost-or-damaged-tax-refund-check/0...
Starting on Monday, March 15 you will be able to use the IRS Get My Payment site to see what is expected for your 3rd stimulus check:
https://www.irs.gov/coronavirus/get-my-payment
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
