Whoops, this needs to be updated.
"the distribution, having been made in the form of a check, was misplaced and
never cashed" is one of the reasons you can get a waiver of the 60-day rollover rule. See question 6 on this page "How do I self-certify that I qualify for a waiver."
https://www.irs.gov/retirement-plans/retirement-plans-faqs-relating-to-waivers-of-the-60-day-rollove...
https://www.irs.gov/pub/irs-drop/rp-16-47.pdf
You must complete the rollover within 30 days of discovering the error. Call the issuing bank and ask for a new check. Then call the IRA you want to receive the funds and ask if they will accept a late rollover if you provide a copy of a self-certification letter that follows the model letter in IRS revenue procedure 2016-47. If they won't accept a late rollover under the model rule, you may need to find another IRA bank to accept the check. (Once the check is accepted in bank A, you can do another rollover to bank B if bank B is your preferred bank, but this time do a direct transfer.)
You submit the self-certification letter to the IRA trustee, you do not include it with your tax return, but keep all your records for at least 6 years.
