I checked the wiki thoroughly, and there's no information available about a Browns vs. Bills preseason game or Shedeur Sanders' performance in one. The wiki covers Browns news through early June (OTAs and minicamp), but preseason game results from August 2026 aren't in the database yet.
What I can tell you from the wiki is that the QB competition between Sanders and Watson was still unresolved as of minicamp — Todd Monken said he'd need to see full pads and preseason games before making a decision (from the Shedeur Sanders page). So if that game happened, it would have been a key evaluation moment for him.