Of course Beyonce was lip syncing!
Let me clue you in -- almost all artists lip sync these days. We call it "singing to track," which allows the artist to sing over top of their own pre-recorded version of the song.
As a matter of fact, there is a bit of an art to matching your performances, complete with dramatic pauses, facial expressions and exaggerated movement to make it really seem like you are singing live.
The bigger the venue, the higher the chance it's not 100 percent "live." This is not to say Beyonce (or any other artist) can't sing live, just that they prefer to control the environment in a studio and remove any chance of a mistake when the world is watching.
We expect perfection. No singer is perfect.
Sorry to burst your bubble.