What if the drugs were in someone else's bag?

A closed container belonging to someone else is meaningfully different from a substance in plain view in a shared space. It cuts against both elements the State needs.

Knowledge is harder to prove when the item was inside something you didn't own and hadn't opened. Control is harder to prove when the container belonged to another person present.

What can undercut it: statements placing you with the bag, evidence you handled it, fingerprints or DNA, the bag being within reach and open, or an account that changes over time.

The practical point is that ownership of the container is a fact worth establishing early and precisely. Whose bag, who bought it, who had been carrying it, whether anyone else could say so. Those details get vague quickly, and they're often more useful than anything discovered later.