WordNet (r) 3.0 (2006):

unidentified
    adj 1: not yet identified; "an unidentified species"; "an
           unidentified witness"
    2: being or having an unknown or unnamed source; "a poem by an
       unknown author"; "corporations responsible to nameless
       owners"; "an unnamed donor" [syn: nameless, unidentified,
       unknown, unnamed]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "unidentified":
   able, anonymous, cryptonymic, cryptonymous, enigmatic,
   incalculable, incognito, incognizable, innominate, mysterious,
   nameless, puzzling, sealed, strange, unacknowledged, unapparent,
   unapprehended, unascertained, unbeknown, uncharted, unclassified,
   undefined, undesignated, undisclosed, undiscoverable, undiscovered,
   undivulged, unexplained, unexplored, unexposed, unfamiliar,
   unfathomed, unheard, unheard-of, uninvestigated, unknowable,
   unknown, unmarked, unnamed, unperceived, unplumbed, unrecognized,
   unrevealed, unspecified, unsuspected, untouched, virgin,
   without a name