When the enemy laner goes back and they do not have Teleport, push the minions to their tower as fast as you can (without missing any CS). You can then either go back and buy or roam to another lane. If you go back to buy, you can then choose to either go back to lane or roam. If they do have Teleport, you can still push it to their tower but they will most likely Teleport back to lane and not miss much CS.
You play Sion so this is pretty easy to do, you go back to base and run bot lane, stand back so they can't see you. Then Ult into Bot lane and hopefully you will get some Kills/Assists. Then you can either help push that Tower down or go back to Top lane.
As a Top Laner you should always be keeping your eye on the mini-map for potential Teleport plays (assuming you took Teleport). Bot lane is probably the best lane to Teleport to because there is a potential 2 kills and a Tower.