Rev 11:19 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.

Perhaps it is in heaven.  Probably though, the one on earth was a copy of the one above in heaven. Since the temple, and all it's instruments, and all it's services were mere shadows, copies, and symbols of the reality of heavenly things.  So to, probably is the ark of the above scripture the real one in heaven which the earthly was merely a copy of.  What do you suppose is in the real one in heaven?

Exod 25:10 And they shall make an ark of shittim wood: two cubits and a half shall be the length thereof, and a cubit and a half the breadth thereof, and a cubit and a half the height thereof.
11 And thou shalt overlay it with pure gold, within and without shalt thou overlay it, and shalt make upon it a crown of gold round about.

The Ark is stored in a government warehouse and has been there since roughly 1939.