I dunno. Maybe. 5,500 years is a very long time. Even the arid 'Valley of the Kings' has probably had flash floods from time to time. They have evidence of that in some of the lower tombs they've found, if I recall correctly.
Whole societies of ancient Egyptians passed through the ages without the later ones knowing much about the previous kingdoms. Looking back on them today, they all seem the same to us, but their greater civilization lasted thousands of years.
Egyptian antiquities were lost to grave robbers and tomb raiders -- sometimes almost as soon as the vault was sealed, other times they probably came several hundred years later. Some are certainly still undiscovered, and some may never be found.
If that car would have sat hidden and dormant in Oklahoma, it would have been uncovered eventually when ground was broken for a new 385,000 square foot WalMart SuperMax in the year 2125. You'd really have to try to keep something hidden in modern day America for it to have a chance of never being found and preserved intact. I can't think of too many places like that in the USA, but I would suggest the Superstition Mountain range if I were going to try.
True--nobody's found the Lost Dutchman mine.
Or if they have, they're not talking.