Hypnagogic Twitches

Last night, I was WILDing on my side, and just about to slip into sleep. Suddenly, my whole right shoulder jerked backwards at a joint that doesn't exist, and smacked my girlfriend in the face. Strangely, it felt like my wing flapped back, not my shoulder. My girlfriend mumbled something like "you just hit me with your wing, what the F* was that?"

I certainly don't have wings, and I don't think my shoulder can bend at the angle I experienced, so obviously this was a hallucination. Anyone else had an experience like this, where they get hypnagogic myoclonus in a body part that doesn't exist? It felt so natural to have opposable shoulder blades.