One option may be to get your 8710 from your PP checkride if possible. That would be a government document where the FAA or its represenative (DPE, etc) would have verified the exact hours that were in the very logbook that was lost. Like many little problems, this is likely more about how you handle it than what it actually is. If you can't get a copy of that 8710, maybe a sworn affidavit or at least a notarized statement that the missing 60 or so hours from that logbook are true and correct, etc.