Stephen B. Ringle, Registrar/Preparator   writes:

I used to do that, but our director did not like the blatent designation
"missing", so I was forced to use more circumspect means of irecording
and identifying what we could not readily locate.
This was, to me, a hassle.  I appreciated the politics and diplomatic
aspects of what the director was saying, but from a pragmatic
collections management point of view, needed a quick and easy means
of listing what was currently lost or missing.
>>>>>>>

How about "Location Unknown" ?  It doesn't jump out on reports like the
word Missing.