The last mention of the presence of the ark is in King Josiah’s days around 622bc (2 Chronicles 35:3). From then on it is not obviously in anyone’s presence. And the prophet Jeremiah said in 3:16:
In those days, when your numbers have increased greatly in the land,” declares the Lord, “people will no longer say, ‘The ark of the covenant of the Lord.’ It will never enter their minds or be remembered; it will not be missed, nor will another one be made.
So it was probably concealed during Josiah’s reign.
It does get a final mention in a most interesting place:
Then God’s temple in heaven was opened, and within his temple was seen the ark of his covenant. And there came flashes of lightning, rumblings, peals of thunder, an earthquake and a severe hailstorm. Revelation 11:19