You should not rely on the receipt on a FinderException to tell you that an entity does not exist in the DB. For a CMT bean, the container might throw this exception before the DB is accessed.
You could instead not use a finder, try and create the entity in the DB and handle CreateException. The problem is that the client cannot be sure what happened as the container may throw this exception after the transaction was committed. So, on balance, I guess the least worst approach is to use the finder method.