Well that brings up a pretty common mystery, for which there is no pat answer and nobody can ever fully explain. You are not alone. The most common speculation is either too much or too little water, or some of the trace elements are out of range. You might try a soil test. Has this happened before? Some varieties are more prone to do that. I had a couple that bullnosed every year, and they were small enough to move, so I put them elsewhere and they are better. Another is about 50 years old (almost impossible to move) and never opens its buds, and I have about decided to give up and graft something else on it. If it has never happened in previous years, it may be climatic, but otherwise you may need to do some investigation.

You can read a good discussion thread on this subject, with more suggestions as to cause and cure on the American Camellia Society bulletin board, see link below. Click on the Bulletin Board and find the thread, "Anyone have a cure for bullnosing."

Here is a link that might be useful: American Camellia Society

I don't know if this will help, or even apply to you. Here in the UK this can be a problem in some areas. It is caused when there are overnight frosts, and if the camellia is in a spot where it gets the early morning sun, the conbination of frosted buds warming quickly can cause them to fall. I'm lucky we rarely if ever get frost and camellias are very cheap to buy here 3' ones from as little as $2.