Thanks to everyone!
I just leave the BCL15 on the E-PL1 body, and fit a regular lens when I want to shoot with something more sophisticated. I have the same problem with the Lumix G 14mm ... It looks like a body cap and I misplace it all the time.
(I ordered an E-PL7 body and I like the BCL15 so much I've ordered a BCL9 Fish-eye to go with it... 🙂
G