I'm just a layman on these things (I'm sure ArchaeologyChick will show up to clarify) but yeah it was my understanding that shifting sands bury things; Pompeii was covered by volcanic ash, etc. Ever watch someone's old shed break down? It just gets buried somehow.
Interestingly, it seems to work the reverse also. Cecille B. DeMille's first Ten Commandments (1923 or so) was filmed out in the CA desert and boasted a complete and accurate recreation of an Egyptian kingdom, including 35 ft tall pharoah statues and 100 ft tall columns, etc. After filming, Mr. DeMille ordered the site buried and employed much dynamite to accomplish this. It has now become an active archaeological dig, as the constantly blowing wind from the ocean is uncovering it.