Tough call, the picture is still a bit small and blurry.
If I was taking a guess I'd maybe go with Thamnophis atratus zaxanthus (Thamnophis atratus zaxanthus - Diablo Range Gartersnake) did it look like this when you were holding it?

(borrowed the photo from California Snakes Photo Index)

I'm going on the dorsal stripe being more orange and the sides being yellow. Do you know where it came from? The snakes range is a great way to tell what it is, because obviously if it came from the east coast it's not likely to be one of these.