unrecallable
ungraspable
draw a blank
blank out
block
forget
unrememberable
unrecollected
anomia
unremembered
oblivious
blank
antimnemonic
unrecalled
unrecallably
on the tip of one's tongue
misrecall
lethologica
unremembering
anterograde amnesia
nonremembrance
nonmemorized
immemorable
unexacted
unmemorized
unknowable
nubilous
misremember
misremembrance
unmemorable
unsurmisable
brain freeze
unspeakable
unharked
presque vu
adiagnostic
historylessness
forgetful
detaillessness
forgettability
inconceivable
unrevealable
nonknowable
brain cloud
unknowledgeable
unimaginativeness
memory of a goldfish
ignorant
unchronologically
unwitting