Anthony, I'm so sorry to hear that Neko has diappeared. Have you searched all garages, basements, etc.
I know how you feel, I have had 10 cats over the years and one of them dissapeared without a trace. At this time lots of cats in our neighbourhood were missed and you could read in the newspaper that there were pet-catcher for the animal experiment laboratories on the road
Really don't want to know what happened to Cleo
But another one came back after seven days missing :) So there is still hope. I keep my fingers crossed.