Verify ECDSA signature without data
It is not possible:

Let $d_A, d_B$ be distinct private keys. Then

$$
  s=k^{-1}(z+rd_A)=k^{-1}((z+r\;(d_A-d_B)) + rd_B)
$$

So the pair $(r, s)$ is not only a valid signature for the public key $d_AG$ and the (partial) hash $z$, but also for the public key $d_BG$ and the message hash $z+r\,(d_A-d_B) \pmod n$.

So in many cases (if there are no restrictions on valid values for $z$), every valid signature $(r, s)$ ("valid" for some public key) and every public key $d_AG$ there will be a message $M$ such that $(r, s)$ is a signature for $M$ under $d_AG$.