It never left Jerusalem.Personally, I think that it exists because the trail ends at 538 BC when the Babylonians conquered Jerusalem. The Babylonians did not mention the Ark in their list of Temple “war booty” items that were taken.Also, many of the Levite priests of the Temple were never mentioned again in the Bible. I think that the Knights Templars were right on the spot but lacked the necessary tools of excavating it.They spent 10 years excavating that particular area of Jerusalem where the mosque is now located.Now there is a mosque on top of where the the altar of the first mount and the location of the Ark is probably somewhere underneath.Maybe in some hidden shaft underneath the mosque. I think that it would be found if there is a systematic search of the area. If it is found it would be an historic event.I think the Muslims are worried that it would be found one day
One of my Jewish Professors said that the Rabbis in Jerusalem know exactly where it is and are waiting for the right moment to reveal it. They probably discovered the chamber some time after 1967 but resealed it.