the answer is...biffle never went down a lap. fox has some of the worst racing production i've ever seen...biffle stayed on the lead lap the first time he came into the pits because he had such a huge lead. he came into pit road the next lap for his stop-and-go, but the yellow came out before bowyer passed him, so he stayed on the lead lap.
my guess is that bowyer, who apparently was going faster than nascare wants people to, passed biffle before greg got out of the pits. since the field was frozen while he was still on the lead lap, he got to go around the pacecar to correct scoring, not as the result of a lucky dog. the other lead lap teams made pit stops, biffle stayed on the track and reassumed the lead.
if the fox broadcasters had done their jobs, they would have told us how everything played out instead of showing replays of bobby hamilton, jr's, problems the past few weeks.