Size of the buds when they went missing?
Squirrels? Birds? Drought-stress?

Any chance of pictures of a damaged bud?

Not sure what your area is like, but here (northern VA) we're overrun with deer and they LOVE to gnaw camellias (esp smaller plants) all the way back to the branches--some of my younger camellias get entirely stripped if I don't protect them.

sounds like deer to me, too.
some years are worse than others around my yard. they usually don't bother the leaves or branches on mine but they will take almost every flower bud, open or tightly closed, from the shrub.
i have had success in years past by putting out strongly scented bar soap shavings wedged in the branches. have to do that before they discover the flowers, though.
irish spring is a soap i used which kept them away. if you cut the soap pieces large enough, they will stay there through several rains and melt into the branch crotches.

No deer here, only squirrels. This plant has been growing here many years and never before been bothered. Have no idea what has changed.

Squirrels will eat the buds here. I see bits and pieces lying on the deck rails where they 'sit and eat'.