I feel your pain! Once Ozzie and I were walking at our LOCAL upscale park and he disappeared into the bushes for a long time!! I called and called and finally had to go in and see what was going on. There he was with his face in a pile of what I thought was very stinky animal poo. He had a huge smile on his face, like "AAAHHHH....best thing I've done all day!!" A lady came over to see what was going on and she told me "Oh, you have to be careful. That is where the homeless people frequent when the restrooms are locked!" Several thoughts crossed my mind at that point.
1. I could just leave him in the park. He is so cute that I was sure someone would pick him up and take him home to clean him up. I could rescue him later!
2. Tie him to the top of the car (a la Seamus) for the ride home, prior to hosing him off when we got home!
3. Abandon altogether and get a new clean dog.

But of course, none of those things happened. I just put him in the cargo of the car on a big towel, a clothespin on my nose, and then hosed him off when we got home. This was followed by a bath in the dreaded bathtub, which was subsequently cloroxed, along with my clothes and the towel from the car, prior to washing.

I guess human poo is about on the same level of excellence as a treat/perfume as cat poo! From this point on he is on leash as we walk past the outdoor toilet!