I have found several web pages that explain how to find if a user is invisible by sending them a message. One of the websites had a link to a page explaining a way to detect an invisible user without having to message them, but the link is broken. How can it be done?
If you want to find say firstname.lastname@example.org is invisible or not. Open your Gtalk application and type this email address in top search textbox.
Click the profile, it opens in new window as usual. Click on the down arrow button in the top right corner of the window, and you can see Go off the record link there.
And type any chat, say “hello”. You will get a red text showing the “person is offline , can’t receive the message right now ” implies the person is offline
If this message does not appear, it means the user is invisible