It's happened to the best of them and some without the catalog as this guy here. Jay- Z was recently in concert in England and while performing "No Church In The Wild", he forgot the lyrics. Check out the footage below!

Jay Z forgets lyrics in the middle of concert:

Of course being the professional that J is, he didn't lose a beat. You have to think about the music that this guy has from his own music to features. It's bound to happen at one time or another, and more then once in some cases. Props to the homie for delivering a solid new album Magna Carta Holy Grail, and be on the lookout for him when he comes to a city near you.