Grump - I did the EXACT same thing... I was lowering the vehicle with the jack, the phone rang, I talked for 5 minutes, and forgot to tighten the lug nuts. The bad part was that it was on a Jeep Wrangler with 4.5" of lift and 33" mud tires at 70 mph! That was scary.
The tire stopped rolling when it hit a sign almost 1/2 mile down the highway. When it happened, I had my little digi cam so I snapped a pic. For your enjoyment...
I have proof:
