Great question. I made a study of this in college with a high-speed camera and a few of the guys on the Texas A&M golf team. Anytime there's grass between your ball and club face, there will be very little spin on the ball. We found "Flyers" are caused by the there being a enough slightly moist grass behind the ball to act like a lubricant between the club and ball. However, in the case of flying lies, the grass is light enough so as to not slow down the club through impact. The ball shoots out faster and  lower with less spin because of the lubricant effect. Now, if the grass is fairly light weight, dry and "wispy", the shot will probably not be affected much as it will still spin. However, if their is a lot of heavy, tough and or moist grass, the grass will slow down the club and it's anyone's guess how far it will travel.

first thing would be is the ball sitting up in the ruff. if the ruff isn't too thick and the ball is sitting up its probably a flyer. winter ruff usually provides alot of these. 

cheers 

simba