Only the IRS can answer your question. You'll need to contact them by telephone to find out the status of your returned refund check. See the information below on how to contact the IRS.
https://www.irs.gov/help/telephone-assistance
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***