Use the search bar in the top right hand corner. If you can't find him, well then you haven't configured your database correctly in order to find him. I have no idea which country he's from, but if you haven't loaded that league it is entirely possible, and reasonable, that he hasn't been loaded into your saved game.
No one can get him. Its one of the flaws in the game. Earlier versions allowed you to see stats on Directors and Chairman and choose your own Director of Football. Since 05 I think, its not possible. I would love this feature brought back. This is the prime example, an assistant goes onto Director of Football and may return to assistant or go onto Manager at some stage. Toshack did this (Director - Manager) and I'm sure Dennis Wise wont stay as Director forever.
Go into the editor and remove him from his post at real Sociedad, save the editor under a different name using the save as feature then restart a new game. He will then be available as a free but you'll have to be quick because I imagine he'd be a popular choice as an assistant. Rememeber to fire your current assistant if you have one.