They have a process for exactly this.

https://www.irs.gov/faqs/irs-procedures/refund-inquiries

If the check was not cashed, you can get it canceled and a new one mailed.

And yes, I've dealt with the IRS a few times some of which they owed me money. It is a bureaucracy, but the process will work even if it takes a bit of time.

yep, done that a couple of times. No response, no progress, nothing. FWIW, my wife did get them on the phone once and she was told we needed to prove we never received it -- that was years ago now.