I'm sorry to hear about your missing kitty. The uncertainty must
be really rough. Don't lose heart yet--a lot of cats wander off,
and some go missing for weeks or months only to return safe
and sound. Cats have a wonderful sense of direction, and I
believe it bodes well that your cat has a year of outdoor
experience behind him. I know that you've already started
looking for him, but in case you haven't seen it yet, there's a
good page here with advice on finding a missing cat:
http://www.mspca.org/site/pp.asp?c=gtIUK4OSG&b=127205If you know your neighbors, you might also ask around to
find out if any other cats have gone missing. Most likely
the two cats disappearing was a coincidence, though.
Do check the local animal shelter frequently.
There are online websites that offer free "missing pet ads." The
local chapter of the ASPCA for whatever state you're in might
let you post a missing ad, or offer advice on what to do.
Good luck. Don't give up on Leon.
-Sarah