Why did Apple Mail delete my entire inbox and starred mail?

All of my Gmail Inbox messages were suddenly deleted both on my computer and phone. This includes my Starred emails. They are not in All Mail, Trash, Spam, or anywhere else I checked. All of my mail from every tab (Primary, Social, and Promotions) was deleted. I did not Archive or move the emails in any way. I've learned from the Google Help forum that this is caused by updating to iOS9 and is a problem with Apple Mail. Any help on this issue and how to recover lost emails is appreciated.