Hmmmm I don't have a key to my 5 month old Prius

It is in your fob.

 

look on the left corner and you'll see where it says "push" push it in and the key will extracted it's self from the Bottom. when you look at the bottom of the unit there's a slot for a key ring that's your key once you pull it out

 

No need to be embarrassed, salesman did not show you and you have not read your manual.

 

You should also find that after you take the key out, you can put just the end of it in the slot and twist it to separate the two halves of the fob. This gives you access to put in a new battery when it's needed.