Gota agree with Jim here - the FAA may very well be your best friend on this anticipated purchase.

When an experimental aircraft receives its AW certificate, the facts of the AW inspection and the original limitations for the aircraft are permanently filed by the FAA as well as the identity of the original builder and history of ownership - I believe these will be in Oklahoma City unless this has changed - in any case, your local FAA District offices can facilitate procurement of this information. As Jim says - these guys really are here to help and my experience with the FAA is like Jim's.

It may or may not be a red flag when logs get lost - they can get lost in one of two general ways: 1) Accidentally (the dog ate it, misplaced in an estate); or, 2) Intentionally (to get rid of the aircraft's history). Having said that - lack of aircraft logs can be a benign situation where you may be able to piece together enough info from the FAA, contacts with previous owner/builder, etc.