When you bought this camellia, did she have flowers? just as you like them, the variegated pink ?
If she didn't have flowers, yes, then .... perhaps a mistake on the label?? It happens very, very often!! :(
Otherwise there are several camellias which are able to change colour of their flowers and can come back to the beginning, once more. It's only a question of the weather you had last year, and, of course, of the variety which has that mannor.

Which variety does "Sieboldii" actually refer to (it is not a valid name) ?
If it really does means 'Sieboldii', which is an old synonym of 'Leeana Superba', you should get an cup-shaped imbricated red flower (with erected center petals rosy red and pink variegated).

If it means 'Tricolor' (aka 'Tricolor (Siebold)'), then it is normal : this a very unstable variety, which produces many sports. But you still can easily tell if you have a Tricolor, because of its charateristic wavy and slightly curled leaves.
You may wish to have a look on the pics I took on our 'Tricolor' plants :
http://nerolie.net/images/camellias/tricolor.htm
These are only a few examples of the many variations you can find on one single bush of 'Tricolor'. Perhaps you will find variegated or striped flowers with the next blooms :-)

If it's not one of them, could you take a pic of your bloooms ?

Here is a link that might be useful: C. japonica 'Tricolor' flowers

Hi. I had this same issue (with a different camellia variety). The flowers were red with white splotches when I bought the plant, and this year, it has blooomed with solid red flowers. I have asked three specialists about this, and these are the results of my inquiry.

Head Nursery buyer at Berkeley Horticultural Nursery: The plant could have revered back to its original genetic (the form it was before it was hybridized to produce the variegated color).

Nursery Information Desk at Filoli Garden National Trust Park: It could have formed a "sport" of itself with a different flower color. But she said this would normally only happen on one branch at a time.....not the entire plant at once.

Specialist at UC Davis University: the variegated forms are extremely unstable and are affected by climate conditions. Those conditions may have been present in the nursery where you purchased your plant (and the nursery where it was grown), but are not in your garden (at least they were not this year). She said it was likely that the variegated condition would eventually return in future years as climate conditions vary every year.

Some changes here : the 'Tricolor' and 'Lady de Saumarez' know have finished flowering. But on 2 of the 'Lady de Saumarez' I have seen yesterday flowers of 'Fred Sanders' (bigger, shiny and fimbriated). When I look closely at the leaves I can tell the difference between 'Lady de Saumarez' (same leaves as 'Tricolor') and 'Fred Sander' (slightly bigger, smaller serration, dull green). I am quite surprised as these plants have always been supposed to be 'Lady de Saumarez'... But Fred Sander is an other sport of this family :-)

indiatree, each of the specialists were right, but each answer applies to different cases.

the first one refers to an unstable chimera which reverts to solid (and then can't go back to the chimera). As an example, 'Comte de Gomer' and 'Comte de Gomer Rubra'.

The second one refers to a new mutation within the terminal bud, which produces a new sport. Example : 'Ville de Nantes' is a sport of 'Masayoshi'.

The third one refers to unstable chimeras and mutations which repartition and/or expression can vary when the flower bud develops, depending upon the wheather. Examples : 'Tricolor' and 'Lady de Saumarez' (which usually produces 'Lady de Vansittart', 'Lady de Vansittart Rubra', 'Lady de Vansittart Blush' and variations of 'Yours Tuly' on one single bush).