Sorry to hear what happened. I've had a few panic attacks in various toilets before myself so can totally relate. It's not nice.
My personal weapon against anxiety attacks through social situations has been exercise. Sounds simple but it's very effective for me. I'm sure it could be of at least some benefit to anyone that can motivate themselves to do it.
Get your yourself a bit fitter (I go jogging/cycling), then a few couple of hours before the social event exercise vigorously. Obviously if you plan on going to salsa again you're going to need to save a little energy for that.
It's a LOT harder for your body to become anxious after you've done a lot of physical activity. There's only so much adrenaline that your body can make/use in a certain time period. The lessening of the physical anxiety will in turn help your mental anxiety as they are so closely linked, and have a vicious circle effect on each other.
Don't write off the idea before you've tried it because it sounds simple. Exersize is one of the most powerful anti-anxiety agents going.
You may want to consider some kind of therapy to if you haven't already done it. If you don't think you could do that in person, there's good books such as...
...That you may be able to take something from to.
I hope things work out for you.