As others pointed out, "memory wipe" is a broad category, but assuming that this is about episodic memory:

How about sending yourself a letter via delivery service on a specific date in handwriting + audio-recording? This of course completely ignores any other faked messages that would need to be discarded, but even with only episodic memory loss, I assume I'd be so confused as to be easy game for even the most incompetent scammer.

If this is about formal guarantees, we need to have some more precise ideas about the "memory wipe" and the adversary in question. In the most general case, likely game over.