One option if you lose your logbook and have no records of your own is to ask your flying club(s) (OK so it won't work if you're a in a group) if you can go through their copy of your records. A friend of mine did this a few years ago when his flight bag (with logbook inside) was stolen from his car. He managed to reconstruct most of his logbook - the only bits missing where a few flights he'd done with other clubs.
Obviously depends on the records your club keeps, and probably not practical if you've been a member of several clubs over the period concerned.
Brooklands