Has anyone, anywhere ever found buried whole aircraft, crated or otherwise ???
Yes: In their search for Weapons of Mass Destruction in Iraq, the American forces found Mig 25's completely buried in the desert sand.
Why bury aircraft?? It's beyond me, I can't imagine resurrecting a Mig 25 after a year or so incarcerated under the sand - surely the restoration cost and effort would be more than going to the Russians and asking them to lend you more money to buy new Migs? That is, of course, assuming you came out on the right side of the battle in the first place!
Why bury a Spitfire, even if you just want to dispose of it?