Does it look something like this one:
If so, yours is bleached...and will need some TLC before it becomes healthy...
It honestly sounds like its bleached out and stressed by your description. I've only seen one healthy white photosynthetic anemone, and it was an enormous H.magnifica anemone that had been in captivity for over 10 years. Anemones will shrink in size when starving for nutrients....basically surviving by devouring its own tissues...
If its still sticky, you can nurse it back to health. It will most likely darken up. The one in the picture above turned a boring brown with green high lights. The gorgeous blue seen in the picture above was not visible after the anemone regained its zooxanthellae. It took close to 6 months for that to happen, and I fed it 3-4 times weekly.
The largest Long Tentacled Anemone, (LTA for short, Macrodactlya doreensis specificly) I've ever seen was only about 12-14 inches in diameter. However, MojoReef, (admin here) told me about a friends M.doreensis anemone that was fed 1-2 whole cocktail shrimp a week that grew so big that it took over half a 90 gallon tank...approx 24 inches in diameter. What I've noticed with my anemone's is that the more frequently I feed them, the larger they grow. If I want to restrict growth, I cut back on the feedings...
Ocellaris clowns will sometimes be hosted by M.doreensis anemones, but it is not their natural host...some people have luck with it, others dont. Give it time, try to get the anemone healthy first, and go from there.
Nick