Lost Log Books

I should already know the answer to this but I don't so here it is -
what do you do if log books for a glider have been lost w/no hope of
recovering them? How can AD compliance be assured w/o doing them all
over again, assuming that a simple visual inspection by a qualified
A&P can't confirm it? What about airframe hours -particularly if
limits could be an issue? Repairs that are obvious (or maybe not), yet
have no documentation? Who would sign off on an annual w/o access to
the maintenance history?

Mike