Not unless they're in a shared channel with you. You should be verifying the correct address, even if there is a nickserv, since people don't always have an enforcement enabled which prevents someone else from camping on the nick.
If you know the correct address, and they're in your IAL, you can find the nick that way.
//echo -a $ial(*@*irccloud*,0) shows how many nicks match that address mask, and //echo -a $ial(*@*irccloud*,1).nick shows the 1st matching nick. The ial seems to sort by the 1st letter of their nick.
