I will assume you can't see the messages so have assumed they were deleted.

This forum has had a lot of folk of late complaining about not being able to see all their messages because they have used the quick filter bar to reduce what is seen to only messages with attachments or that are unread. Is that your issue?

Otherwise, right click the folder. Select properties and then choose repair.

Thank you for the quick response. I did not use the quick filter. I tried your suggestions but it made no difference. Any other ideas?