I'd think it depends on the amount of time you've spent imagining this experience in the novel. If you have had enough time to vividly imagine the entire experience, none of the questions should catch you by surprise and you could answer almost as if you were actually there.

Regarding con-artists, yes I suppose it comes down to whether they can be as quickly imaginative on the spot as most people who are truthfully recalling an experience. That's probably where the inaccurate 15% of results come in.