i had a similar problem... you said that "his picture is gone and its not linked anymore" - this means there is still a contact for him in your contacts app, just with no picture?
if this is the case, try this: go to contacts, click on your friend's entry, then click on the black space with some logos under "joined contacts" - is there a "joined contact" with his Facebook picture? probably not, since it isn't showing up anymore. if you click on "join another contact" on the bottom of the screen, does a contact with his Facebook picture show up? if so, join that contact to the other one, and it should solve your problem.
i had to mess with this for a couple of different problems - one was the problem that you described, and the other was that Facebook was syncing incorrect Facebook friends with my google contacts (i.e. - i have a few mike smith's, both in my google contacts and on Facebook, and Facebook could not tell who was who, so i had to do it manually).