Not really at the moment, unless you put something in party finder and wait for them to see their name or something. Once you interact with them you're able to whisper them/join a LS together. You could always try to find them on the lodestone, see if they're even on Gilgamesh anymore. When 4.57 hits, the data centers are getting split up and the world visit system goes live, but that's limited to servers in whatever data center you reside in.