He hitched a ride
The bus to the park was coming at quarter to nine, so he got down at about 8:20 to make sure he didn't miss it. The bus didn't show up. It turned out that the message that he couldn't retrieve was to tell him that the bus wouldn't be coming until 10:30.
He spotted Mike Euenback(?). He said, "Mike, where you going?"
Mike said, "I'm going to the ballpark."
Jerry said, "How are you getting there?"
Mike said, "I got a car."
Jerry said, "Now you got a passenger."