Smartform table - header and footer disappeared

I have a Smartform with a table element. When table was created, there were automatically 3 nodes added - Header, Main Area and Footer. This nodes cannot be added or deleted manually, I believe, they just appear with the table.

However, after experimenting with some changes in the form (which included adding and removing sorting and events on sort start/end), I notice that only Main Area element is there but Header and Footer are gone. Unfortunately, I haven't registered the exact moment it happened.

Has anyone seen anything like this and is it possible to repair the table? I searched the notes and forum but haven't found any mentioning of such effect.

Thank you.