It's a circular that's stuck somewhere in the yarn pile... I gave up knitting on straight ones years ago, except for the 11s I bought when I was in another state from my stuff. After working on them for a couple days, I remembered why I didn't like them and went and bought a circular.
I did see a site where someone does collect odd needles (like 2 or 3 dpns, singles) and you can trade or buy. That may be the same one you're remembering, I don't know what happened to it.