Bryce Laspisa, 19, disappeared early Friday. His overturned SUV was found at a boat launch north of Los Angeles.
Sheriff's deputies say LaSpisa was able to break out the back window and walk away from the crash.
According to officers, dog teams tracked his scent to the edge of the lake.
"That's what I'm hoping for, that maybe somebody took him in, doesn't know who he is and weren't smart enough to call the hospital or police," said Brian David, uncle.
Laspisa and his parents moved from Naperville to California. He is attending college there.