Whew! Sounds like you got to do at least some of the race course. I wouldn't want to mess with that clay when it's wet, either. Slimey. I am glad you got to see that you are by far not the only one that walks stuff or has the good sense to know when to bail.
Sorry to hear about your knickers but glad it was only the knee....a friend crashed on the downhill and ended up flashing us with one cheek the rest of the race.

It doesn't surprise me that the organizers didn't cancel. Tread Lightly isn't much thought of, much less followed, around there.