That was the point; Tini poked Kamina and was carried along when Kamina teleported. In the games, when you go to rescue someone in a Mystery Dungeon, you use your badge to teleport them out...however the badge's abilities are slightly inconsistent; while you can teleport out of a dungeon after completing a mission, you need an Escape Orb if you want to leave without completing a mission first. Since the games failed to firmly establish what the badges could and couldn't do, I felt that two people teleporting to a guild with the same badge at the same time wasn't too much of a stretch