Hello @scombs426
That is very odd! Sorry that you are running into this issue.
To confirm, there is not a setting that would hide the annotations that were added, if they were done in Speedgrader.
Were the annotations done in something such as Google LTI assignment? If so, there appears to be an open known issue HERE that is impacting External annotations in the DocViewer.
It's worth noting that If you start to make an annotation but do not submit it before the session expires, the annotation will not be saved. Submitted annotations are saved and are not affected by the session limit. Canvas will display a session expiration warning at 9 hours 50 minutes, followed by a 5-minute and 1-minute warning until the 10-hour limit has been reached.
-Colton