Yea, you must be an oper on the IRC network to be able to see if a person used a /whois command on you. OR on a few networks i've seen an oper can actually turn it on for specific non oper nicks.
The majority or networks use a private notice that looks something like this.
[9:23pm] -xxx.xxx.xxx- *** Notice -- /WHOIS command used on you by: <censored> (xxx@xxx.xxx)
