It depends on how important the thing was. We memorise what matters to us.
Certain, seemingly trivial things can become ' important' in context - so perhaps the quiz wasn't.
Well in the spirit of the thread, and the substantive subject under discussion, could we assume that the quiz night
WAS important ... or, rather, something that happened on the quiz night was important ?
Purely hypothetically let's imagine the following scenario :
During the quiz, or some time later, Kate and Gerry have a blazing row ... I don't know, let's say because Gerry had been paying too much attention to the attractive quiz mistress ( purely hypothetical, remember ) ... and Kate stormed off back to the apartment on her own
Now, let's assume that the tapas friends would be reluctant to tell the police about that incident because they felt it had nothing whatsoever to do with the crisis that unfolded two days later, but were afraid the police might 'make something out of it '
So out of loyalty to Kate and Gerry, they decide it is best not to mention the incident, which they feel is insignificant in any event
They cannot 'lie' to the police though ... so they collectively 'forget' all about that night ... indeed, they even forget what night it was
Given the research you are are refering to, is there a possibility that collective forgetfulness may be an indication of lying ... where the subject forgotten
IS significant ( as in the hypothetical example I have given ) ?