Typically borderline, but essentially these sorts of entries are harmless, and if one or more editors think it's worth having, I won't block it.

gg5 examples

I still feel this isn't really needed. Literally "not existing in memory".

@@ -14,5 +14,5 @@
-<pos>&n;</pos>
-<gloss>not as (far) as one can recall</gloss>
-<gloss>not as one remembers</gloss>
-<gloss>not as one have experienced (seen) before</gloss>
-<gloss>not in (recent) memory</gloss>
+<pos>&exp;</pos>
+<pos>&adj-i;</pos>
+<gloss>not in one's recollection</gloss>
+<gloss>having no recollection (of)</gloss>
+<gloss>having no memory (of)</gloss>

記憶にない	218207
記憶に無い	52100

OK

@@ -5,0 +6,3 @@
+</k_ele>
+<k_ele>
+<keb>記憶に無い</keb>

I think this would be worth having. Not 
entirely obvious.

記憶	22020815
記憶にない	218207

While not uncommon, it's still only 1% of the use of 記憶. In fact to me the "not in (recent) memory" meaning is the most obvious one. I'm inclined to go with Robin on this.