Caricaturists, contracts, & cancellations

Infrequently, (actually VERY infrequently over the years) I have been in a situation where I've been contracted to do a live caricature gig, which then gets cancelled for whatever reason...this happened to me last night :-(
I was supposed to draw at a company picnic, which was going to be held at a minor league ballpark during a game. Early in the afternoon, I got an email from the agent saying that the client had cancelled (not postponed) due to expected heavy rains coming our way. While I certainly understood the client's need to do this, it's always a bummer when Mother Nature intervenes to the point where no one gets a caricature!
This is where contracts come into play with any kind of professional entertainer whose time is scheduled out to various events. The agent is taking care of the situation for me in this instance, but I thought it was worth bringing up for anyone interested in the business aspect of caricaturing!
Yes, it's not ALL about the drawings :-O
My own personal contract for a live caricature performance states the obvious, of course--- who, when, where, my rate, what kind of party it is, my deposit policy, and my cancellation policy.
I always get a non-refundable deposit to book a party. This lets me know the client is serious, and it also protects me if the event gets cancelled. When I commit to a client, I am then turning down all other inquiries for that time slot. For last night's event, I turned down two or three other offers after I had accepted the agent's booking. If the event cannot be rescheduled to when I am available, the deposit is my payment for holding that time. Luckily, this happens sooooooo rarely, but it still needs to be in black-and-white print so that everyone is on the same page!