This is one of the exception regularly comes when we do custom development and create custom aspx pages. Everything works fine and no code issues but still this exception comes.
Error occur as :- No item exists at http://sitename/pagename.aspx?Id=2.It may have been deleted or renamed by another user.
The issue can be easily solved by renaming the querystring parameter to a different name other than Id
After renaming the parameter the Sharepoint page will work as expected.
The issue occurs due to conflict of querystring parameter Id with sharepoint list Id.
Hope this helps and save you from killing so much time to know the problem.