The FORM is really there but you got to notice that this page is within a Masterpage. The FORM is declared within the Masterpage.
The current page you posted will be shown within the masterpage on the ContentPlaceHolder. So actually the form will be posted, does the customer get any response from the page?
Besides the response, the page will be posted back to itself (i think) after the button is being clicked. The data in the form will be lost if no viewstate is being set. Viewstate can be switched on and of. Either you can check within the form_load() event if the page is postedback. The actions can be to fill a new viewstate with the current field-values and reload the values from the viewstate after the page.IsPostback. That depends on how the fields are responding on the userinput. Reading your code the fields don't respond after the text has been changed so you can fill a viewstate in the button_click() event.

Regards,
Richard
The Netherlands