Something similar happened to me a few years ago; I was on a "trip-to-nowhere" when I went across an antique shop. I kinda like antiques.
So I stopped and went inside; cool old stuff and all, a few hot-wheels. I inquired about model kits; they said that they had a few a while ago, all sold-out.
I then mentioned that I liked old buildups, to which they replied with surprise that indeed they have a box full in their attic; been there for years!
When they brought it down, it was full of built kits bought BEFORE 1959!!! And all decently built, with original boxes;
Revell 57 Ford Country Squire wagon
Revell VW van (the one full of windows)
Palmer 59 Fury convertible (ONE OF MY HOLY GRAILS!!!)
Palmer 59 Corvette
And quite a few others.
I only wanted about half the kits in that box, but they so wanted to get rid of them all that they made me a deal.
:-)
On my way back home, I had to stop every miles or so to check my trunk, to make sure I wasn't dreaming. :-)

So, always ask for old buildups; you never know what treasures will come up.