Which password manager? I know BitWarden uses a "recycle bin" concept, so if you log into vault.bitwarden.com and look in the bin, maybe your deleted passwords are there.
Since when do police send letters advising of a crime? A "warning letter" for a relatively minor traffic offense maybe. But a hit & run? Seems to me they'd be paying a personal visit.
Before going too far, ask yourself whether this letter is even legit. What is this letter asking you to do?