Poison Oak?

We finally visited the San Francisco Zoo, after having lived here for four years.

The weirdest thing about the Zoo had nothing to do with the animals - it has to do with the fact that I saw what I believe to be poison oak growing right outside one of the animal exhibits, where people can easily touch it. In fact, as I was gaping at the plants and second guessing myself, a woman did touch it - she leaned over, grabbed one of the vines, pushed it out of her way, and then turned around and looked at us. I jabbed Dear Daniel in the ribs with my elbow and hissed, "Did she just touch POISON OAK?"
"It looks like poison oak," he said.
"It IS poison oak," I said, "But there's NO WAY they'd let it grow right here at the Zoo, right?"
"I dunno," he said, "This is kind of the back of the Zoo where all the reject animals are."
After the woman walked away, I went really close to the plants, and I got a good look, and I SWEAR it was poison oak.

I've never had poison oak, thankfully. It grows all over Northern California, and I camped and backpacked with my Dad from a young age, and I've known what the plant looks like since I was a kid. And I'm extremely cautious about it. It's supposed to be the most painful thing you can possibly imagine, outside of childbirth. And the thing with poison oak is the poison is an oil which does not rinse off, and you end up touching yourself all over and spreading the oil around, and then you get these huge, itching, pus-filled welts.

I still can't figure out if there was poison oak at the Zoo - it seems like that would be a liability issue. Maybe it was a plant that looks exactly like poison oak... does such a plant exist?

Another weird thing - I live in a National Park, and there is poison oak EVERYWHERE here. I stick to the trails when hiking here; I'm no fool. From the trails I can see it crawling up trees, forming itself into huge mounds, and growing amongst the wild blackberry bushes. Little fingers of it reach out to the trails, too, so I always wear long pants when walking and hiking.
So I found out they're holding this Bay Area Orienteering event here this weekend. Orienteering is this "sport" in which you're provided with a topographical map, and landmarks, and you have to navigate your way to the landmarks. At each landmark, you obtain proof that you were there. The object is to get to all the landmarks and reach the end first; it's a race. You have to figure out if you're willing to walk the long way around or go charging through a stream to get to a landmark faster, etc.
It's like you're the star of your own adventure movie. On the event website it warns, "Wooded areas may have some poison oak."

MAY have SOME poison oak?! I don't see how anyone can hike anywhere in the forest here off-trail without getting COVERED in poison oak. Well, I wish them luck with their orienteering...