The application you were running was closed because you were disconnected from it for a long time.
You disconnect from the application when you close browser, or close the lid of your laptop, or put your iPad to sleep. When this happens we keep the application running in the cloud so that you can connect back and continue working. This way you do not have to worry when your connection gets dropped and then restored. Also this allows you to disconnect from the application and then connect from another device.
Recently used section of the web site will always show how much time has left before the application will be closed if you disconnect from it.
When you are done, it is always recommended that you close applications with File/Exit.
Learn more about running applications on rollApp.