you lost your 8606 but that doesn't mean the IRS lost it.
If it makes you feel better, make a small non-deductible contribution (if allowed) like $100 and file form 8606
showing your basis + 100.
file 8606 showing your basis, many people do this even though it's not required.
With no contribution Turbotax won't include 8606, you'd have to file on paper.