Dynamics AX 2009 Enterprise Portal Troubleshooting Blank Page Issue

We have implemented Dynamics AX 2009 EP portal for one of our business. Users log on to the EP to create/edit/view their timesheets. Recently, we got this issue where suddenly the Edit timesheet page got disappeared. Whenever the user goes to view/edit timesheet, the page was blank.

Solution:

a. Checked the Event viewer and security logs but couldn't find anything.
b. Restarted IIS but with no luck.
c. Restarted AOS, restarted the web server but still the same error persisted.
d. Checked in sharepoint virtual folder and found that the Edit Timesheet.cs (C# page) file was not there.
e. Finally, went to AOT > Web > Web Files > Page Definitions > EditTimeSheetpage and right-clicked to deploy the same to the web server.

This solved the issue, but still wondering how the page got disappeared!