Per Google Maps, there are 2 "Summit Trails." One is listed as "summit trail trailhead" at 37°50'38.6"N 121°56'57.3"W, the other is outside the park at 2410 Diablo Lakes Ln (technically outside the park and off a private road). If you follow ST down all the way, you'll get to the first one. Google maps gets the name of the trails wrong. If you are wondering where the car is or why that last stretch of trail seemed unfamiliar, this might be why.