Just spoke with Mr. Brost (sp?).
His house is the 2nd to last west one ... most westward one near the fence more specifically.
That may be where our food vendor drove if I understood correctly ... over the lawn and broke a check/backflow valve apparently.
In any case, he had a spare one and fixed it himself - about an hour he said. I asked for a cost and how we can reimburse him but he said it was no big deal and refused to take anything. He just wanted to let us know what had happened.
I think we will have to ensure any future vendors, competitors and guests will know where to go (e.g. a better map?) to come and watch, participate or otherwise. We may still not be able to circumvent something like this happening again but perhaps we can minimize the risk of it happening again.
In any case, Mr. Brost was very cordial and friendly on the phone and said no offence was taken and all is ok. He mentioned he realizes that there are many people who come to these and it is hard to control everyone (my paraphrasing).
So this is all settled now.