Actually, some believe the Ark was taken by Egyptians,
or hidden by Jeremiah,
or destroyed by the Babylonians, etc.
Here’s a link about how the Ark was supposedly in Ethiopia:
To summarize some parts of the above article,
Ethiopians usually say (from the legend of the Kebra Negast, the Glory of Kings)
that the Queen of Sheba fell in love with King Solomon when her servant returned from him so she went to Jerusalem to see him and remained there for six months.
Solomon also fell in love with her and on the day of her departure, he ordered a royal meal for both of them and both made an oath not to take anything from each other by force.
The King intentionally left his bowl of water next to the queen’s bed, so that when she awoke she would take a drink, thereby “taking” what was rightfully the king’s and breaking the oath.
The Queen realized this, and she said, “I have sinned against myself, and thou art free from [thy] oath.” Then is said that, “He permitted her to drink water, and after she had drunk water he worked his will with her and they slept together.”
Nine Months and Five Days after going back into Ethiopia, the Queen gave birth to a son named Menelik. At the age of 22, Menelik traveled to Jerusalem to meet his father for the first time.
And, at the hands of his father, Menelik became the king of Ethiopia and founder of the Solomonic dynasty.
When the young man departed from Jerusalem, Solomon commanded the nobility of Israel to “give [to Menelik] their children who were called ‘firstborn.’” The clever ruler saw an opportunity to establish a second kingdom.
With this, Menelik and his new subjects departed for Ethiopia. But what Menelik’s companions failed to mention was that they had made off with the Ark of the Covenant from the Temple of Solomon. Indeed, they only told Menelik when they had reached “the water of the Ethiopia.” The news—while surprising—didn’t turn the young man back to Israel; he continued his trip with the relic under his protection. The journey of the Ark recounted in the Kebra Nagast ends in Ethiopia after a brief stop in Egypt.
Hancock also theorized another theory how the Ark came to Ethiopia.
Sometime during King Manasseh’s reign in Jerusalem from 687 to 642 B.C., Jewish priests removed the Ark from Solomon’s temple since Manasseh had converted the Temple of Solomon to pagan worship and installed a pagan idol—a blasphemy for those devout Jews who considered the Ark the touchstone of the Lord on earth. Hancock speculates that the horrified priests removed the Ark from Jerusalem entirely.
He claims the priests took the Ark and settled in Elephantine, a small island just off of Aswan, Egypt. There, the Jews built a temple to house the Ark—the ruins of the temple are visible to this day.
There the Ark remained on the island for some 200 years.
Then it was moved to the Island of Tana Cherkos where the Jews are said to have also built altars of sacrifice for the Ark. It was brought there since at that time, Tana Cherkos is the only island monastery in existence. (There is also stories that Our Lady stayed at Tana Cherkos for three months and ten days.)
It stayed there 800 years before King Ezana finally brought it to Aksum.