I am sorry this happened. But I will say that if you have a dog who is very protective of toys - or has any type of aggression towards other dogs he plays with regularly like the snapping/snarling you mentioned - that you should NOT take him to a dog park, or let him around other dogs for play. You may think the woman is in the wrong, from her point of view you could be in the wrong. She probably expected your dog would be friendly as you had him at a dog park. I think that is a fair expectation on her part. Again, I'm sorry it happened, but it sounds like the whole time you were a bit on edge thinking it was a possibility, which in my mind means you should never have been there in the first place.
No , I want to clarify I've done this a lot , with a lot of dogs . You instantly know when there are dogs around that are going to be trouble I know this and I saw it, prior to seeing these dogs we've been playing frisbee with the digs that were there to begin with with no issues, it only happened when these three familiar dogs came into the picture I saw the behavior change in the dogs there hair was up and you could tell they were going to be a reaction.