Tree rats, squirrels and deer are the usual suspects. If their primary food source is lacking this time of the year, it is possible that they decided to eat your flower buds for ack of a better thing.

There are traps and such for squirrels out there that you could get. And you also could feed them corn away from sensitive garden areas; however, no one who has proposed that solution has ever been able to document whether that might make them stay in your garden instead so, I have not tried that. Keeping the dogs loose seems to help in my yard.

probably is squirrels. in some years, they take some of my camellias' buds but the damage is not that bad.
i trap and release them far away from my place.
it got so bad one year that they were eating no only my plants (which i could have tolerated) but then decided to chew holes to access the roof area. actually, 7 juveniles took up residence under the roof that year and i finally got them all out.
i live in a rural area and can shoot them legally which is what i had to do because of the sheer numbers.
you can find a catch-and-release trap at co-ops, feed and seed stores and maybe hardware stores.
personally, i would not offer them an alternative such as the corn, thinking it would encourage even more of them to come around.
another option might be to do what the folks with bird feeders say they have had success with: a cayenne pepper mix applied to the food source but might be a lot of effort dealing with rain washing it off.

I haven't any problems w/ squirrels in my yard- my cats make that very dangerous. Squirrels don't even bother my bird feeder. A cat or two would take care of the problem...
But, all the buds on one of my camellias fell off a couple mos. back- just lying on the ground. The other three in the row are fine. I don't know what caused that. Brandy

You have a few "choices", Brandy.

* The very tiny camellia bud mite infests the flower buds and flowers causing them all to brown out and fall. Early in the year, they like to suck the juices of leaves (top and/or bottom) and can chew on them. Large infestations will produce web like material. Spray a miticide in May and then two weeks later to catch the ones hatched from eggs. If detected later in the year, they can feed off flower buds causing them to drop.

* Temperature changes that happen too fast for the plant can also cause flower buds to drop. For example, a large sudden change (up/down) in temperatures in Fall or Winter. Try to stop fertilizing in July/August so the plant has time to harden before winter and go dormant.

* reaction to insecticides either directly on the plant or indirectly (you spray the plant besides the camellias and the winds blows the insecticide towards the camellia). Check insecticides to prior to using to see if they say that they can cause bud drop. Apply them on days with no wind (if you can).

An infestation of the camellia bud mite would be visible and I would expect that you would have said something about the leaves. Because you did not, I think the problem was weather related.

Two winter seasons ago, we had warm temps in the 70s through mid-December. Then a cold snap dropped the temperatures to the low 30s and they stayed there for almost a week. I lost all flower buds in all plants (well, I did have two flowers by two separate plants but that was IT!).

Luis

Squirrels have been destroying my single Spring blooming Camellia as well. I've seen them in action so its definitely squirrels. There must be a major food shortage this year. They tore off buds, chewed into them a bit, realized they weren't that great for eating, dropped them and left, returning several times. I'm going to a nursery in the morning to try and get some Anti-Squirrel/Anti-Rodent spray (its made out of pepper and other substances generally although I don't like the kind that contains putrifescent egg solids, i.e. rotten eggs) but they've done a ton of damage already. You can also get these products online. I don't know how well they work but I'm going to find out.