Box online missing files or folders

Hi Shoni, 

Welcome to Box Community and glad to assist! 

Note: When items are deleted from a collaboration folder, both the owner and the person who deleted the item can recover the items from the Trash. 

You can filter content by items you own, or by items you’ve deleted.  To do this, directly beneath the folder label (Trash), click the Items I Own (or Items I Deleted) down arrow.  Then click the option you want.

To restore specific items in Trash:

The steps below apply whether you’re selecting from search results or from all Trash items.

1. Hover to highlight the row of the item you want. The More Options ellipsis (…) displays.
2. Click the ellipsis (...).  Then: 

• To return the item to its original location in Box, click Restore.

3. At the prompt, click Okay.

You can visit this article in reference to these information. 

Hope it helps!