Thumbnail source missing

I have a db with multiple folders containing rtfd files that have text plus jpg or tif images.

To help identify files within a folder, I drag one of the images from within the file to the thumbnail pane on the Info panel.

One of these files has an image in the thumbnail that is now missing from the body of the file. Must be a broken link but I don’t know how to fix it. If a thumbnail is just an alias, where is the original image?

I looked in package contents and can’t find it anywhere. I searched on Spotlight.
I ran Verify & Repair; ran Disk Utility; nothing.

I tried to drag the image out of the thumbnail and back into the body of the file.
I made the mistake of doing Data:Thumbnails:Update and now the thumbnail consists of the page with rtfd written across it so now I’ve lost both versions of that image.

I’ve had problems with unstable thumbnails before (wrote in last November 2013), and thought I had it solved by unchecking things in Preferences: Media, but this is a new one. I really don’t want to lose that image. Could use Time Machine, but don’t want to restore an old db that doesn’t have more current information.

Any ideas?

The thumbnail of a DEVONthink record (group or document) is stored as binary data. It is not a link or alias – it is a copy of the image. A script to grab that data and create new rich text document with it seems to be feasible. I’m just mentioning this because someone in the scripting forum might want to pick up that challenge.

if you select the document with the interesting thumbnail, one approach is to use this snippet to grab the thumbnail:

set theThumbnail to thumbnail of the content record

(Don’t have time to fiddle with the rest right now.)

Most likely the image was deleted from the original file by human error. If you have a backup copy of the database in Time Machine or elsewhere, you might find the original again. Before playing with any scripts on this, make sure you have multiple safe copies of the original.