Two things stood out to me in the Frank-on-a-bike photo: He's in an extremely low gear (small chainring up front, large cassette cog in back), indicating he was riding slowly and was in no hurry (at least at the time this photo was taken), so he was way ahead of schedule at this point.
Also, I can't see a bike lock of any type, either on the bike itself with a frame clamp or pannier, or in the form of a chain wrapped around the top tube, or on Frank's person either. Before this photo was discovered, the cheating-with-a-bike scenario had me wondering how Frank secures his bike to ensure it's still there when he returns to it after crossing a timing mat. In most urban areas an unsecured bike, even a crappy one, will vanish in seconds if it's not locked up, or even if it's locked up with a less-than-sturdy device. Frank would also have to ensure that there was something in the vicinity of a timing mat, such as a fence, lamp post, etc., that he could safely lock the bike to. With no lock in sight in that photo, I say he either had a confederate to monitor the bike for him while he dismounted to cross timing mats, or he was so brazen that he left the bike so close to the timing mats that he could keep it in sight while just running a short distance to have his chip recorded. Given Frank's character, or lack thereof, I wouldn't rule out the latter.
And as other posters have mentioned, other courses where it wasn't possible to cycle so close to the race would have required different cheating strategies, not necessarily using a bike.