Like what someone said earlier, it depends on the situation, the type glider, and the price. Having gone this route numerous times restoring vintage power planes, the lack-of-logs can or can not be a big deal. If its a schweizer, metal/tube/fabric, no logs is not a big deal. If its a glass bird, depends on the model, the seriousness of its ADs and the price. If they’re giving it away, then a close look see may be warented. I picked up a very nice HP14 with partial logs for a very reasonable price, well worth the effort involved in doing the research.
Dan