It may happen that you fall in a cave and can't get out because you haven't bought the right drill yet.

Just press 'T' to teleport back to the surface.

In the top-left of you screen is a teleport recharge timer showing how long you must wait before you can teleport again.

You can only teleport when your weight is less than 10KG.
So you may need to drop some items before you can teleport.

Changed the User Interface a bit.