The name you cannot recall may return after the person who needed to hear it has left.

The name arrives an hour too late, in the car, when it is no longer any use. Recall runs on its own schedule and is not available on demand, which is why the thing you needed in the moment shows up when the moment has closed. It is an ordinary property of the machinery rather than a sign of anything wrong.

When it happens, sending a short message afterwards costs nothing and often means more than getting it right at the time. And in the moment itself, saying that you have lost the name is far less awkward than the manoeuvring required to avoid saying it.