TC, I went through Terminus Cave too and managed to get out using an Escape Rope. However, if you came in without using Rock Smash, then you can leave without using it. Just try to find the Karate People and Hikers, they should be close to the exit.
You're wrong. The exit is in Alaska. Walk thousands of miles TC. Hard work, I know.
-----Official Pikachu of the Pokemon Y board----- Playing) Pokemon X and Y (3DS)
I seem to be stuck, too. I walked in as far as I could, fought a Hiker, then I got stuck in front of a boulder I need Rock Smash for. So I turned around to leave, but there are ledges blocking me from going back the way I came in.