As said, it is very easy to 'forget' in the studio. When I did Pointless, in preparation I preprogrammed myself that if any country based question came up, to chack and see if Comoros, Kazakstan or Kyrgystan fitted the question (as all 3 were normally pointless). Final round we got a country question and ... all three went out of my head...didn't even think of them! So much for preparation!!! Luckily my brother thought of Panama (even though I'd been there 3 months earlier!).
BTW, when Mt Everest was first surveyed, the height came out at exactly 29,000 feet. The surveyors thought "no one is going to believe us" and made the official height 29,002 feet...to sound more accurate! As the mountain grows 1/8" a year (due to tectonic upheaval), at the moment the official height is 29,029 feet (which is really easy to remember for quizzes!).