I believe it was taken back to heaven, & it is there to this day; because of this scripture :
Revelation 11:19-19
King James Version (KJV)
19 And the temple of God was opened in heaven, and there was seen in his temple "the ark of his testament" : and there were lightnings, and voices, and thunderings, and an earthquake, and great hail.
I believe it was taken at the time they took Elijah . It was taken when Elijah went to heaven; in the whirlwind/ chariot of fire.
2 Kings 2:11
King James Version (KJV)
11 And it came to pass, as they still went on, and talked, that, behold, there appeared a chariot of fire, and horses of fire, and parted them both asunder; and Elijah went up by a whirlwind into heaven.
I believe it is in heaven. I believe that it is not on Earth anymore .That is my opinion about it .