You may have accidently deleted the desktop.ini file. The folder will then show up only as "Documents".
Do you have 'Show hidden files' enabled in Folder Options (Explorer - tools - Folder Options - View - Advanced Settings)?
If the desktop.ini isn't there, right click an empty spot inside the folder, click New - text file, copy and paste the two lines above in it, save. Then rename this file to desktop.ini.
Is it just the name that changed? Still shared, still the same icon?