I propose an error message appearing when a student submits a discussion post after the discussion availability passes. The error message would allow students a chance to copy their post from Canvas before it disappears.
A student started working on his discussion post at 11:40 PM. The discussion was set to be available until 11:59 PM. The student worked on his post for 20 minutes and submitted the post--or so he thought. When he later looked at the discussion, he saw that it was closed and noticed that his grades did not show his discussion submission.
When I talked to Canvas support, the support specialist did not see any submission information on the backend. It appears that the student's submission went into the abyss without him know it. He understands that he will need to recreate the discussion but has requested that we help get safety measures in place so that other students don't encounter this issue.