It looked to me like a small .22 or .25 automatic. I think it was bigger than the baby browning but maybe smaller than a Walther TPH. It looked like an older model. Brown grips, single stack mag. It was in a tiny rectangular leather holster that barely exposed the grip area and the barrel. If I wasn't on the lookout for OC'ers, I never would have even noticed what it was... it blended in very well with the other "belt pouch junk."
The grip color and shape seemed to resemble this Colt Junior picture I found on the web, but all I could see was the back of the pistol... maybe a tad larger, and possibly striker fired, but I could be wrong: