It's mean to hold things from your children.
Marc sees his daughter's phone on the floor where she has dropped it, and he picks it up and puts it in his pocket.
Marc wants to teach his daughter to be more careful with her things.
Marc tells his daughter that he found her phone on the floor and tells her he will give it back if she promises to be more careful with her things.
Marc keeps the phone in his pocket, and he lets his daughter think that it is lost when she comes looking for it.
Mary is happy and relieved to get her phone back, grateful to her father, and she keeps her promise to keep better track of her possessions.
She is genuinely panicked when she thinks she has lost her phone and all she learns when he tells the truth is that she can't trust him completely.