If something like this happens again, try the following:
DON'T CLOSE THE BROWSER WINDOW/TAB where you had been working on your report. DON'T DO ANYTHING MORE (such as trying to navigate back or using the same tab to visit other sites). It is OK if you had already tried going back to the previous page. WHAT'S DONE IS DONE. JUST LEAVE IT ALONE NOW.
DON'T TURN OFF OR RESTART YOUR COMPUTER.
Open another browser window/tab if you need to do other things, such as periodically checking to see if SASSIE is back up.
When SASSIE is finally working, use a NEW WINDOW/TAB to log in to that company's SASSIE.
ONLY AFTER YOU HAVE SUCCESSFULLY LOGGED IN, go to the window/tab where you had been working on the report and try to GO BACK. DO NOT JUST RELOAD THE PAGE.
I have often been able to revive my report this way. Usually, the need arises because I was automatically logged out of SASSIE after more than 30 minutes of inactivity.