This happened to me and my sister when we lived in Thirsk the North of England in around 2002. We were in a sports centres car park when my mum left us in the car and went in to check opening times for the pool.
My sister and I (I then was around 12 she was about 10) saw a man walking strangely across a field adjacent to the car park. We were laughing between ourselves at his ridiculous outfit: a top hat and knee high boots, and the fact that he was walking very slowly and proudly across the field holding a cane. He had a small black dog with him. We watched as the dog disappeared into a hedge in the middle of the field. As we were wondering why the dog hadn't reappeared on the other side of the hedge, the man also walked into the hedge and didn't reappear the other side.
We carried on chatting and messing about for around 10 minutes, and then our mum came back to the car. We immediately started telling her about the man and dog, but when we looked back to show her where it was, the field had changed into a woodland area. There was no open field, no hedge, no man, or dog. We were in disbelief and very confused as to what happened.
To this day, I have no idea why we saw that man or the vanishing field, and why the rest of our surrounding -- the car and carpark -- remained the same throughout the incident!