Phantom dog paws

While this is not a big deal; nonetheless it can be disconcerting. While reading my E mail, today in the Library, just before 8:00 pm, I distinctly felt two dog paws on my rightside pants leg. Often, if my dogs need to go, they will let me know in this manner. I immediately put my hand down to stroke which ever dog (we have two) was asking. My hand met with blank space and the paws released like the dog had jumped back down. There was no dog there, nor was any even close. My wife insisted they were both in the kitchen with her. Just an interesting observation.