No they don't know, however expect that they will ask.
In which case if you could have flown with them, lie, telling them you did.
-And know the flight times you could have taken.
Air NZ asked me, and despite the reason being both cost and especially schedule as to why I didn't, I overheard the comment about me that I clearly didn't think it was important enough.
As has been pointed out before with interviews, they will go hunting for any negatives they can if they want to.