A lot of channels are generating views from clickbait thumbnails. Is there a way to scan a video beforehand and determine the timestamp of the thumbnail, if it is even in there?
Partial answer from Bellingcats's Advanced Guide on Verifying Video Content:
There is no easy way to determine which frame a video will automatically select as a thumbnail, as Google developed a complex algorithm for YouTube to select the best thumbnail for an uploaded video (for more on this, see the Google Research Blog entry on the topic here). Perhaps the best tool to find these thumbnails is Amnesty International’s YouTube DataViewer, which generates the thumbnails used by a video on YouTube and allows you to conduct a reverse image search on them in one click.
This gives you the thumbnails, but not their timestamp in the video. You would still have to go through the video to locate that frame.
No, this would be not possible to achieve by any easy means. Also, verified YouTube accounts are able to upload custom thumbnail which may not even be from video footage.
Create a custom video thumbnail
To upload custom thumbnails, you must have a verified account.
Best you can do is to fast-preview the video on mouse-hover (eg. before clicking on the video and adding unwanted +1 view) to determine if the content of it is matching the thumbnail context.