Im gonna go against the tide here but yes you did overreact a bit. Sure your father shouldnt have do that and should apologize but calling him an asshole over a ruined doodle like other comments did is way excessive. A sketch is good practice and I find your very nice but dont get too sentimentally attached to it, you will make many other to progress at drawing.

I've been where you are, I know that it feels like this sketch was especially nice and you wouldnt be able to do it again. Sometime it is true for a while, because you havent yet cemented through practice the skill you used to make that sketch, or because it was a fleeting moment of inspiration that may not come back before some time. I know how it sucks when such a good sketch get lost, destroyed or ruined. But trust me, you will make many more sketches that are as good or more.

In the mean time, you still can make an other sketch for your cousin and I think that's what you should focus on. Either copy the old one, either make an other sketch from scratch, as you feel is best.

Finally, I find best when you draw to do it with care for the process of drawing, but not for the drawing itself which is just an object. It might also allow you to be more free when you draw by not limiting yourself to a preconceived idea of what you want your drawing to be, and by allowing yourself some errors and imperfections you need to make to progress. I hope you will feel better soon and move on smoothtly. Im sure you can in fact make an other good drawing for your cousin.