“Last Kiss” was never intentionally released to the public.
Members of Pearl Jam’s fan club are often sent songs that are unavailable to the public or never publicly released. Wayne Cochran originally recorded the song, and J. Frank Wilson & The Cavaliers then rerecorded it in 1964. When Vedder heard that version of the song, he brought it to his band and they decided to record their own cover. Eventually, radio stations obtained the recording and the song started to gain popularity. It was finally released as a single in 1999 and later appeared on Lost Dogs and Rearviewmirror: Greatest Hits 1991-2003.