Check your extensions, you (or one of your colleagues) may have accidentally remove VSE 8.5 (NAP/Extension).
You just need to re-check in the packages and you'll see VSE8.5 again.
Although, im not sure if the previous customized policies for 8.5 that you had created will appear once you did the re-check in..i think you will have to redo all the policies again..
Check your permission set - it is possible that it is missing the VSE 8.5 permissions.
Did the dissapearance happen when you installed VSE 8.8 into EPO?
Although I still had 8.5 policies they were all read only and corrupt after I initially imported the VSE 8.8 extensions....