Here's how to find your Evernote attachments.
• Open an attachment
• Command-click the title to see the path of the file
• Choose .evernote and you'll see the folder with the attachments.
(Then I moved the external-edits folder to the Desktop, Quit Evernote (Ok to attachments message), relaunched, Quit, problem gone, put external-edits folder back into .evernote folder and all is well.)