Some NDAs treat the existence of the NDA as part of the information covered by the NDA.
Now you're scaring me.
Anyway, I fail to see the logic of this, as the existence of an NDA is not one of the facts whose sharing was conditioned on signing it.
Well, by 'existence of the NDA' in that sentence - I don't quite mean just the document - but the resultant 'agreement' between parties. That fits my reading of a recent NDA document I saw, but obviously IANAL.
So, I think it's perfectly fine to acknowledge that LargeCoin was sending out NDA documents for signing, but if you signed it and if it happened to have clauses like the one being discussed, you probably shouldn't disclose anything about what was in it, or that you signed it.