In my pocket. Just like every other phone Ive ever owned in my life.
My wife used to carry her iPhone 5 in her pocket but now carries hers in her purse so now she misses a lot of texts from me. Its annoying but I dont want to say anything because I think shes doing it so I can buy her an AppleWatch.
Send a text asking if she wants an Apple Watch. See what happens next. If she doesn't respond suggest that you changed your mind since she failed to respond in a "timely" manner.