Perhaps the locked item is something to do with the DLC in which you need to complete or do something in to unlock it?
Other than that...
It is hard to figure out what your problem is, is it because of the DLC or because of the save I guess you used from someone elses game?
Problem here with saves is if the save bought all the special stuff with Uplay points and your account hasn't yet, there will be a difference of course, and that may cause problems for you.
as i said i got total 100% sync including in the DLC so the Locked Item not because of that..i completed the game and i unlocked Raiden Outfit..then i downloaded the DLC and which i was need to replace with the file OPTIONS in the same place where the saves located..i came back to the game and Raiden Outfit was locked and i can't unlock it..i think the DLC requires me to connect my account to unlock it again or unlock the item..usually i play "Offline Mode" lately i get problems with my internet so i can't connect to my account or sync my game with AC:Project Legacy Facebook
and please read my topic in F.E.A.R. 2: Project Origin..you might give me aid for the problem i experience with that game..