[1] Buried in a sacred vault under the Temple in Salt Lake City.
[2] Purchased by the Rockefellers in the fourties for over $100M and now located in Jackson Hole, Wy.
[3] Just as the movie indicated, the OSS got their hands on it just before WWII and it has been sitting in a nameless packing box in a government warehouse between DC and Baltimore long forgotten ever since.
I used to take care of the computer network in a series of DOD warehouses on Norfolk Naval Base. I went into one of the giant warehouses the first week I was there to take care of a problem with a Cisco router. The building looked just like that warehouse in "Raiders of the Lost Ark" shown in the last scene. The building was almost a 1/4th of a mile long and it was filled with wooden cases just like the movie. We used to joke that the ark was in that building. :)
There are all kinds of theories.
Personally, I think the Axum one is most likely.
Is this guy a liar? On his website, he says he has NO connection with Indiana Jones whatsoever.
In this article, he is quoted as saying they based it off him.
Jones appears to be a blatant liar here....