His whereabouts have been utterly unknown so far.

迄今他的下落全然未知。

《新英汉大辞典》

Some are now free, but the whereabouts of others is unknown.

其中一些人已经被释放，但是其它被捕者的下落依旧不明。

youdao

He never was found and so the whereabouts of this man are unknown | even today.

他从来没有被发现，所以这个人的下落未知|即使在今天。

youdao

Foley himself is long gone into the parallel dimension of a rehab clinic, whereabouts unknown.

NPR: 'Washington Times' Calls for Hastert to Resign

His whereabouts are unknown but some believe he may still be hiding in Sirte.

CNN: In Gadhafi's hometown, his once opulent house lies in ruins

It said these groups had also detained nine other residents of Wardak, whose whereabouts remain unknown.

WSJ: Afghanistan Moves to Curb U.S. Forces