Good for you!
It appears as if you did all the right things. The knife was stuck in a table, no threat or challenge there. Just close at hand and everyone knows where it is. Your hands on the cane; same thing. It says "I can use them if I have to. Please don't make me." It put the ball in their court. Most importantly, you kept your mouth shut (my big problem). All you did was show them that you weren't afraid and it worked well. There is never any thing wrong with defending yourself.
I really don't like people who prey on fear.

At the very least they think your a crazy old coot in a kilt, and that's not a bad thing!
Bob

ps Old is a relative term. You've only got ten years on me!