Debian :: Lenny : Find And Grep "missing" Files?

i need to scan all files on a dns server (bind 9, lenny) to find a string (192.168) i been suggested to use find with grep i filter out the things i dont need like logs here's the command

find /* -name "slot*" -prune -o -name "var" -prune -o -name "proc" -prune -o -name "log" -prune -o -name "*logs*" -prune -o -name "*history*" -prune -o -type f -print | xargs grep -n '192.168' 2>/dev/null

it show me results with various depth in the directories but it fail to show the occurrence that are in /etc/bind/zones/ if i run the exact same command but with the path being /etc/bind/* the missing occurrence are shown what did i do wrong ?