in his/her pocket
I found this in his pocket.
Il mit le mouchoir dans sa poche.
He put the handkerchief in his pocket.
Ludovic le mit dans sa poche.
Ludovic put it in his pocket.
Il n'a pas sa langue dans sa poche.
He doesn't mince his words.
Ce hamster est si petit qu’on peut le transporter dans sa poche.
This hamster is so small that you can carry it in your pocket.