I've done that to AUS before from IAH. We were on final and turned around when the landing gear headlight didn't come on as we deployed the wheels (something that was broken on the ground at IAH but that they thought was repaired). Suffice it to say I still only got my single miles credit.

Or there was the flight on a 752 from MCO-EWR with the flight map clearly showing that we did 2000 miles. Again, only the original credit (though I think I probably drank sufficient quantities of the supplies in F to offset the incremental extra miles