navigater: The same way as a par 3.fairway miss does not count against you..
Players are supposed to hit the green on Par3s, thus there is no FW hit. The scorecard will show "no hit" but it's omitted in the stats.
navigater: Check the USGA rule's more closely on this one.
Which rule? Please quote it.
To my knowledge, the Rules of Golf do not know FW hits nor GIR nor drive length.
The PGA stats count the drive length regardless where it ends up, bunker or rough, while the common local reglementation of "Longest drive" competitions require a FW hit. I heard once that a fringe hit was denied the prize in an amateur tourney (370 m distance).
So, which rule?