The lab results are in.
A PR firm for Arnold Bakers emailed me a copy of a certificate from Maryland food testing laboratory Strasburger & Siegel stating that microscopic analysis has determined that the "rodent" found baked into a hot dog bun by a Charlotte, NC man was, in fact, "starchy residue."
Specifically:
1. The extraneous matter was conclusively identified as product build-up.
2. The gray streak on the roll appeared to be the result of this product build-up having contacted the side.
3. There was no evidence (hairs, excreta, stains, etc.) of rodent contamination on or in the rolls or the submitted extraneous matter.
Pretty straightforward. No comment from state health officials as yet, though presumably they're still conducting their own investigation, having been totally left out of the loop on this one.