When I did your code, I got an error message saying:

[08:28:07] -> -(Oblivion@xxx.xxx.xx.xx)- Yes (Oblivion@xxx.xxx.xx.xx), I'm an IRCop. Is there something I can help you with?
(Oblivion@xxx.xxx.xx.xx) No such nick/channel

So I made this:

 on *:SNOTICE:*WHOIS*: {
  NOTICE $2 4,12Yes $2 $+ , I'm an IRCop. Is there something I can help you with?
}

I think it works like that because in the SNOTICE saying who WHOISed you, it looks something like:

-irc.trinetchat.com- *** Serenity (Oblivion@xxx.xxx.xx.xx) did a /whois on you.

And you are looking for the person who whoised you, not their address, since it won't NOTICE an address; in this case $2 is the nick of the person.