He listened to my brief run-down of symptoms, looked at my MRI results, tested my reflexes and muscle strength, and said, "Oh, that's easy, you've got meralgia paresthetica." The reason is didn't show up on the MRI is that the nerve is being pinched where it comes out of the pelvis, not where it comes out of the spine. He also said that my doctor did all of the preliminary steps that the neurologist would have done himself (MRI etc.), and was on the right track with the Lyrica, but that being a "primary care" guy, he just didn't have the specialized knowledge to know "diamond-shaped area on my upper thigh" = "meralgia paresthetica."
So I've been given a prescription for one of Lyrica's gentler cousins which should hopefully let me sleep without giving me anxiety attacks. The good news is that this is a condition which responds to treatment and doesn't generally indicate more serious stuff. The neurologist said I should get re-checked for diabetes just in case, and it has been almost a year since I got the battery of tests so I probably will before too long.
He said, "Your search is over, you've got an answer now." :) So hopefully that means the rest will be easy!