User thinks: If I am registered, where's my registration number?

On https://wafertest.debconf.org/register/step-10

You are Registered
Your registration is complete and has been saved.

We look forward to seeing you in Hsinchu.

User thinks: If I am registered, where's my registration number?

"And isn't it going to send me a Proof of Registration by email?"

"With no registration number, how can I later argue that I really did register?"