Both my iTouch 6 G's Have lost their inbox contents

My two iTouches (G6 9.3.1) both just lost all the contents of their inboxes.

The other mailboxes seem normally populated.

My iMac and MacBook (10.7.5) are all normal.

This happened 15 minutes ago.

Any ideas that this non-power user can try to find the lost inbox items?

Many thanks