I agree with the other poster who said you'd have to be behind them for nearly 3 miles assuming you'd otherwise average 30mph and are averaging 12mph behind this bicyclist.

I don't think I've ever had someone behind me that long.

If I had to guess I'd say the guy was probably already almost 15 minutes late, got held up for a minute (tops) and blames the whole thing on that one minute he was held up. If only that bicyclist hadn't been there he'd have left on time for work!