as-yet-unknown
mystery
negatum
heffalump
noncertainty
unk-unk
unknowable
some
inapplicability
inconceivability
undiscovered
knownless
uncongeniality
loss
obscurity
inevident
semicryptic
forthcoming
semiobscure
subobscure
nonexistent
uncertainty
unkenned
secret
vagary
surprise
long shot
inenubilable
undesirability
riddle wrapped up in an enigma
stuff
probable
inanity
extraneity
little-known
some something or other
hidden in plain sight
unploughed
out of thin air
obtuseness
unlikely
mind-boggler
this and that
unintelligibility
enigma
indefinite
whatdoyoucallit
illusion
occludant
misappearance