This happened to me on the Beach at Seaton Crew Nr Hartlepool England.
It was early May last year around 7:30am. I was taking my Collie Suzy for her early morning walk. The beach was pretty quiet at that time of day just a few other dog walkers in the distance, Suzy was off her leash and sniffing around about 20yds ahead of me. All of a sudden I heard a strange kind of whooshing noise behind me I turned to see a Golden Labrador bounding towards us carrying a large stick in its mouth. It bounded past me towards Suzy who seemed oblivious to the Labrador, which was strange as she's usually playful with other dogs. The Labrador then came up to me, I was patting and making a fuss of it and noticed what a beautiful dog it was.
I looked around to see if its owner was anywhere nearby but it seemed to be on its own. At this point it dropped the stick for me to throw it so I obliged and threw the stick 30 or 40 ft from me. The Labrador bounded after it picked up the stick in its mouth and disappeared into thin air. I was of course taken aback by what had happened and still not believing what I'd just witnessed and promptly left the Beach.
I haven't seen the Labrador again since that day last May. I talk to other Dog Walkers who regularly use the same area of Beach and none of them have experienced the Phantom Dog.
Was it a Phantom dog or was it some sort of Time slip I'd witnessed?
Anyway: to the OP, what do you think? Do you think it was real? Or... Something else.
Honestly my gut tells me it was a real dog that took off. But to each his own