Propably you have a “Cancel” action behind the X button. Add a close page button to the page and set this as action for the X button. You can hide the new created by putting it in the footer and hide the complete footer.
The default behaviour for a pop-up layout upon hitting the close button is to rollback the changes and close the page. This means that any data that is not committed to the database yet, will be cleared.
Add a Save Changes button to the bottom of your layout, which commits the data you entered and then closes the page. That will enable you to keep hold of the data when closing the pop-up page.
Also, you could set the ‘Close Action’ in the Properties Window of your page to this ‘Save Changes’ button, if you really want to keep hold of the data when pressing the close button (X) in the top right. My advice however would be to keep the close action as it is and make use of the Save button when data should be kept.
Hope this helps,
It is not a rollback since there is no changes. Data is cleared. All bindings lost.
Before hitting X button (hitting default Cancel button works properly).
After hitting the X button.