How can cocaine get in your system without directly taking it or smoking it?

If you accidentally get some on you, it will, to a small extent, pass directly through your skin and into your system, particularly if you are sweating so that it becomes damp. It will pass more rapidly through mucous membranes, which is why it is often snorted, and why it was originally chewed (as coca leaves).

If you are in a confined space where someone else is smoking it, you will get some cocaine from the "sidestream smoke" that they exhale.