Seahawks wide receiver Percy Harvin beat the entire Chargers defense on a 51-yard touchdown run in the first quarter. But it's clear Harvin stepped out of bounds around the 25-yard line, and the refs still awarded the Seahawks the 6 points.
All scoring plays in the NFL are automatically further reviewed, but even those working in the review office in New York City missed Harvin stepping out of bounds. This gave the Seahawks a 7-3 lead.
Here's his whole run. You can see him step out at the 25-yard line to avoid a defender.