Aha. This one gets the award for least intuitive user interface ever constructed. In fact, it's so confusing I forget it every time I revisit it and have to experiment for another five minutes, as I've just done for the umpteenth time. I presume you have gone to "Revenue Record" and, quite naturally, clicked the "Returns" option on the side bar. Big mistake. That gets you a completely useless skeleton list, where the "Export" option only exports the list.
Instead, as soon as you go to
"Revenue Record" (or if you have already clicked a sidebar option like "Returns", click back on the "Inbox Messages" at the top of the sidebar), and
select the "Search By" drop down on the main panel.
Choose "Search using Document Type".
On the "Tax Type" drop down select "Income Tax".
On the "Document Type" drop down select "Form 11".
Check the "Include Archive" checkbox.
Hit the Search button.
Now you can select your return by clicking on the hyperlinked "Notice No" column and a print view of it will open. (It's not the Form 11 you submitted, but a Revenue acknowledgement with all the details. I don't think there's a way of getting the original, open to correction).
Easy, huh?
(EDIT: Also see the screenshots below for the procedure in pictures)