Sounds like a seizure to me as well. I had a lab when I was growing up that did that, vet said there was really nothing they could do unless they became regular and then they would put her on some medication. I was also hunting in South Dakota about 5 years ago with a Lab that did the same thing. The owner reported that is was just the 3rd or 4th time in 7 years that the dog had done this. This was about how often my lab did it as well. So hopefully it is a one time deal or at least a very rare occurance.