Only forms with `id` attribute are recovered

[achempion]

How to reproduce

$ mix phx.new myapp && cd myapp/ && mix ecto.create
$ mix phx.gen.live Accounts User users name:string
# copy routes from output to router.ex
$ mix ecto.migrate

Now,

• remove id attribute from a form in lib/myapp_web/live/user_live/form_component.html.heex,
• start the server,
• visit /users/new
• and type something into the form's field,
• restart the server.

The form's state wouldn't recover.