Imagine I see you take a rock and stick and tie them together with sinew, which you then use as a hammer to break apart rocks. After seeing you build this devi

Imagine I see you take a rock and stick and tie them together with sinew, which you then use as a hammer to break apart rocks. After seeing you build this device, I then build my own. For me to steal from you, you have to lose something you own, so how have I stolen anything?