In the Content Editor, when selecting media items on the Search tab of the Media Browser dialog box, the following message might appear:
The media item could not be found
The issue happens if choosing a media item that is not located under the path defined in the Image source field.
To resolve the issue, download and install the patch compatible with the affected product version found on this page:
https://github.com/SitecoreSupport/Sitecore.Support.95929/releases.