1. Assume that you will be able to find it. Using words like 'nowhere' and 'impossible' will not help. It is somewhere and finding it is quite possible.
2. Make a list in your head of all the obvious places where it could be.
3. Look properly in each of these obvious places.
4. Retrace your steps. Think about when you had it last and think what you did with it then.
5. Tidy your room. Properly.
6. Ask mum*.
* Note well. Don't ask mum where it is until you have completed steps 1-5.