Sometimes folders in Webmail become hidden if a ‘Disclosure Arrow’ is accidentally clicked. In example A, we see that the disclosure arrow is properly selected and displaying the folders within.
In example B however, this arrow has been clicked to hide all the sub folders. Before worrying about whether or not you’ve lost your folders, make sure that all of these arrows are displaying their contents similarly to example A.
If you still can’t locate your mail, be sure to check in the ‘Deleted Items‘ folder to check for retrieval options.