The photographic evidence is in - my timing chip was lost in the pool during the 300m swim. Mystery solved!
Notice the bare ankles.
One ankle should have a Velcro strap containing some sort of RF ID device that tracks my position and time as a I cross from swim to transition to bike to transition to run to finish line.
A bunch of zeros appear on my official results. Bummer, eh? I had a great time nonetheless.
That's why we do these practice races, I suppose. Learn, and avoid these mistakes on the day of the big race.
Update (3/21): while volunteering at the Texas Double Play Du, I spoke to the team at RunFar, the company that does the event time keeping. It was the same crew who did the Athens race, and it turns out I was one of two athletes who lost their chip at Athens. He said in pool swims, it's usually closer to four or five lost chips. Come Lone Star, I think I might reinforce that Velcro with some duct tape!!