Something can be unforgettable without being accurately remembered.

Intensity fixes an event in place, and it does not fix the details. What you cannot stop remembering may have been reworked repeatedly, sharpened where you told it, filled in where it was blank. Unforgettable describes how firmly the memory holds you, not how faithfully it holds the facts, and the two feel identical from inside.

If you are relying on such a memory to make a judgment about someone, look for any independent record. Where none exists, hold the emotional truth and be careful with the specifics. The feeling can be entirely valid while the transcript is not.