Make sure of the following:
- Both the geodude and the Sandshrew were caught in the Safari Zone
- You have received the National Pokedex from Professer Oak
If you are absolutely sure that you have done these two things, then it may just be that you haven't waited long enough. After completing the second challenge of catching a Sandshrew in the Safari Zone, then eventually he will call you again telling you he has a new idea, and then give you the items.