If you have an open chat window which DCC session is closed, /echo won't recognize =nick as a target anymore. Text simply goes to status as "=nick text".
I've tried using "chat nick" and it doesn't work either.
Although mIRC recognizes the window through other means, it's impossible to /echo there, unless it's the active window and you specify the -a switch or the like.

* cold edits his posts 24/7