I'm not sure what you mean by "missing". The game was never available in the Playstation Store. Most PS3 games released on Blu-ray disks are not available in the Playstation Store. Until a year ago, very few of them were. It is up to the publisher as to whether or not to make a PS3 game available in the Playstation Store. Don't expect this one to be there, now, or in the future.
I think he means the add-ons for the game. I was about to buy some costumes but couldn't find it either. I can only re-download ones that I have already bought before.
-- Update --
I can find the costumes by searching for the characters, so the content is still there but reference to Tales of Graces f to check all it's add-ons are still gone
Ever since Sony "updated" the store, a lot of things have gone "missing" due to, what I believe, their sorting of preferred games, movies, and add-ons being right out front and available. You have to actually use the search function to find a lot of things that have been dumped to the wayside for one reason or another. And yeah, I noticed that not all the add-ons for quite a few games are available through the store.
Gotta say, they ruined a good thing they had with the previous look. At least it was easier to navigate through. I don't really like playing hide-and-seek with this new store.