Some recordings may no longer exist, if they ever existed originally. A Quarrymen rehearsal that was recorded at Colin Hanton's home was taped over. BBC documentation shows that "Sheila" and two versions of "Three Cool Cats" were recorded and never broadcast, but the tapes were likely reused or discarded, a fate shared by some of the Beatles' studio session tapes prior to late 1963. Carl Perkins said that he joined the Beatles in the studio for a late night jam session on 1 June 1964, but this was probably not taped. Several Lennon–McCartney titles were mentioned in a 1960 letter from McCartney, including "Looking Glass", "Years Roll Along", and "Keep Looking That Way", but there is no evidence that tapes were ever made of those songs during rehearsals from that era.