I pupnapped my cousins pup lol!?

Okay so I gave my 11 year old cousin a chihuahua pup about 4months ago, the pup is about 6months now.. Well lately everytime I go to her house I see him wandering in the street, neighbors yard, ect.. & I always tell her to keep him in the yard.. (shes the braty type) & tells me 'hes okay, he always comes back!' It kinda pisses me off cause two years ago I gave her & her siblings a pitbull pup & a month later they lost it, anyways today I seen the chi in the road so i decided to take it home to teach her a lesson & just an hour ago she noticed he didnt come back home, started freaking out, crying.. so now I feel bad lol was I wrong to do this? I just hoped it would teach her a lesson! My grandma knew the whole time & I just had her call her to tell her what I did & why, so do you think what I did was wrong??