You have proof you paid them. Print out a copy of the check from your bank incase they want it. I wouldn't worry about that. I wouldn't worry about any of it. You know they got your return if they cashed your check.
The IRS sent out a lot of letters. The last couple years were a mess and the IRS got way behind processing returns.
IRS suspending notices
https://www.irs.gov/newsroom/irs-continues-work-to-help-taxpayers-suspends-mailing-of-additional-let...
See this CNN article requesting another copy
https://www.cnn.com/2022/02/11/success/irs-tax-letters-suspended/index.html
