I guess you can blame that on one of the Panoz's
The reason given for the retirement was that Biela was on his way in at the end of his 15th lap, but was blocked from getting in the pitlane by a Panoz, so he had to go round again.
As he only had 1/2 pint of go go juice left in his tank, his team immediately started to pack up all the gear in the pits as they knew they were done for.
Personally, I would have thrown the car across the gravel trap into the pits, would have then had a fighting chance at least.