There are different sorts of triggers and symptoms of Anxiety. You've described what I often go through. This wasn't in my opinion an all out Anxiety or Panic Attack. I've had them and honestly thought I was having a heart attack and would die.

My question for you is what did you do and did you find a way to calm yourself down?

My suggestion is to sit down and go over the experience. Was it just the crowd or was there another trigger perhaps (like contamination worries). Make yourself a plan of action for what you will do next time.

For me it is to plan out my outing and shopping trip and stick to that plan. I carry a worry stone. I try to use the same cashier at the checkout. When out with a friend and feeling panicked I use the excuse of suddently needing a coffee or such so that I can temporarily dissappear. I also pull out some of my CBT exercises if I'm worried before I head out.