Cascade stores deleted items in the trash for 15-30 days (depending on settings) before being permanently deleted.
If you have accidentally delete something you can retrieve those assets in the trash.
Note: resored content may need to be republished or relinked to other pages if it was deleted. Check to see if it has relationships or if the asset is still live.
Also check out the retrieving trashed content article on Cascade CMS Knowledge Base.