Maybe it is not a
list of words they agreed upon, but the item before the right answer is a thing Andrew has got, for example, at home. In fact, the first words are somewhat weird things, like "Bavarian Sky", or "a spider", while the last word before the right one is something more "real" than the others.
A simple example:
"Am I thinking of a unicorn?" "Nope"
"Am I thinking of an angel?" "Nope"
"Am I thinking of a pen?" "Nope"The "pen" is the key item
"Am I thinking of (whatever you want)?" "Yes"
Another try:
"Am I thinking of a flying unicorn?" "Nope"
"Am I thinking of an angel?" "Nope"
"Am I thinking of a blue pen?" "Nope"
"Am I thinking of a door?" "Nope"
"Am I thinking of a hole?" "Yes"