From this article on Drudge:

NASA managers were examining whether the lost bolt would be a problem. Space debris can be dangerous if it punctures space station walls or spacesuits and can jam crucial mechanisms. However, spacewalkers have a long history of losing material in space. In July, Discovery spacewalkers lost a 14-inch-long spatula that floated away.

This really makes you wonder what they were doing with the spatula outside the space shuttle. UPDATE: Sadly, it seems there was no barbeque, no “sunny-side up” eggs for breakfast, and no game of Stellar Space Tag, either. Reader Paul L. writes the following about the episode with the spatula in space:

They were testing possible on-orbit techniques to repair damage to the Shuttle Thermal Protection System (TPS), including the tiles and reinforced carbon-carbon (RCC) wing leading edge. Columbia was lost when a hole in the RCC allowed plasma to destroy the wing during reentry. The “spatula” was one of the tools used to apply a patch material being tested (think spackle, but able to withstand hypersonic flight).

That was my second guess.