Exception, Fault code or Error Object

Question

For most cases I find it quite easy to decide whether to return a special value (most times null) or throw an exception.
But this time i have doubts. Imaging a graphical client invokes a server side service. The service delegates the task to a Class which has to create a special entity using given criterias (used for db access) and store the entity in database.
Except for error reporting there is no reason to give a value back to the client.
For some cases the criterias given by the client can be chosen so tight, that it is impossible to create the entity (similar to a database query, which results in an empty set). That means the criterias were not chosen too clever, but regognizing this happens only after invoking the server.
Now the client shall receive a message, what went wrong. But how should you do that?
1. Thowing an exception seems a little rough because no programatical error occurend and the user did not do a predictable mistake. But this would enable a chaining which would be translated into an error description for the client.
2. Using an "Error Object" in cases of a failure and null oder a "Success Object" for success smells like a bad style, but would not interrupt the program flow like a real error
3. return codes ... same like 2, but more stone age .. =)

Answer 1

I say throw an exception. An exceptional case has occurred. You can't say it's unpredictable, because you've just predicted it might happen. Or would it be possible for the UI to simply not allow that state to be reached? I don't know how your users are interacting with the UI so that's your call