Logically, that's just not possible. The presence of something proves that it was there. But how do you prove it was absent? If you didn't observe it, either (1) it didn't happen or (2) it happened and you haven't yet observed proof of it.
Today, it might be possible to disprove Trump's claim for any specific location because everything is on spy cameras. But back in 2001 that wasn't the case.
Absence of evidence is not evidence of absence.