I have a friend that has a particular disclaimer in his contract…in brief it says:
if you have something special that you want recorded at the event it must be written down so that he can bring the appropriate equipment to capture the event. Otherwise he may not have the capability to capture everything they desire.
In other words, if they don’t tell him what needs to be recorded (out of the ordinary), he isn’t responsible for not having the appropriate equipment to cover it (microphones, cameras, etc.)
Oh….and I have NEVER missed ANYTHING at a wedding! No, Honest!!! 😉