There is no way how to ensure both:
- simplicity of an example (i.e. using small numbers)
- that the example cannot be solved by any other means other than that of ECC.
Even if we can not use "affine substitution attack" we still can simply compute points on given elliptic curve modulo small prime by hand and we can solve the challenge again without "touching" theory of elliptic curves.
But it does not mean that it can not be solved like any other securely established system of ECC.
I solved it using adding points on elliptic curves for example.
And anybody who wants to learn something about ECC should do the same, i.e. take a look at the references given at the end of PDF and try to solve it this way.
It is same like for example with RSA.
Give me a toy example of RSA that can not be solved by any other method only the methods by which the standard securely established RSA systems are solved.
Such a example can not exist.
As a toy example of RSA we could take N=pq=4389. Anybody would be able to solve it even without knowing what Euler's totient function is.
If you use bigger primes then probably the attacker needs some knowledge of RSA but the example will no longer be a "toy example".