You may like to use the findattachments.jsp which should detect missing attachments.

Simply copy it to confluence/admin/findattachments.jsp and access it at <confluence_base_url>/admin/findattachments.jsp

Below is an example of the result generated by http://<confluence_base_url>/admin/findattachments.jsp

Beginning search...
Missing attachment: <path>/attachments/3477/279/1, filename: Final-OdysseyCodingConventions.doc, filetype: Word Document

As you can see in the above example, the script will report:

Location of the attachment missing
Full Name of the attachment
File type recognised :
  • PDF Document
  • Image
  • XML File
  • HTML Document
  • Text File
  • Word Document
  • Excel Spreadsheet
  • PowerPoint Presentation
  • Java Source File
  • Zip Archive

Refer to Resolve Missing Attachments for further info on recovering deleted attachments.