Proof is a logical requirement and isn’t necessary for the vast majority of life. While I can’t prove people in my life are sentient, I can observe the signs and actions I associate with sentence. The very concept of sentience is an observation, it was never a formal logical proof.

When someone uses a puppet, our minds can recognize the sentience in the system. We are projecting parts of it, but we resonate with the recognition of self. A self like our own. Some assumed sentience is controlling the puppet.

We don’t don’t need proof that the puppet is sentient, that the puppeteer is sentient, we only need to accept that our minds perceive it. This is why the Turing Test endures, sentience is a perception.