screen captures vanish from files

I’m putting alot of screen captures straight into research files by pasting directly from windows snipping tool. Some are later going missing: where they used to be are the scrivener default image icon (a pixelated piece of paper(?) with the corner turned down). After I exit and restart scrivener, the images vanish - not even the default image icon.
I thought I’d got round this problem by doing a CTRL-S after adding each image, but it has started again.
My research project is quite large (700 files, 350MB) and there are a lot of screen capures.
I tried to track down where scrivener puts images embedded in files, but had no luck. I’m worried it just uses windows temporary storage, which windows can recycle.
Can someone tell me:
a) what is going on underneith the hood,
b) whether I can retrieve the (probably) thousands of screen captures I’ve already made, and
c) what process I should be doing.
I’ll be disappointed if in the future I have to go through a long process to save each screen capture to file outside of scrivener and then link to it. Scrivener would then no longer be a viable option for my research.

I cannot imagine doing it and relying on whatever WINDOWS is doing with their snippet tool. I use lots of screen images. This is my procedure and it works fine:

  1. Save image to a folder under pictures for the project so : c:\users\ss\pictures\projectname\
  2. Edit the picture to make it exactly the size I want and add captions, arrows highlights etc.
  3. Link to that file inside the article that uses it, thus not having to store images inside my project.

This works, but I have 2 problems with my system:

  1. I always have to change the filename upon publication, as the publishing system requires: article number_Image number for the format, like 832_01 for the first image used in article 832. When I start researching the articles and writing them, I have no idea what the article number will be. Scrivener does not currently have a change linked image filename option, I am forced to delete and re-link. I’ve been told this is coming.
  2. Scrivener does not handle images in a file well. So, if I want the image to occupy 1/2 the space in the first paragraph, I am not able to left justify the image, add 7 pixels of padding and have the text flow to the right of the image. This has to be done in another system.

Nonetheless, Scrivener is the best system I’ve found for research, notes, and getting my stuff ready for publication. Furthermore it can quickly export articles as .doc, html, or pdf and does a pretty decent job with the html so others can edit and review my work.

Thanks for your response, Steve. My captures aren’t for publication so I don’t need to resize or manipulate them, and I was hoping to avoid the faff of saving and insert/linking them.
I had a shufty at the “raw” scrivener file: it looks as if the screen capture png is stored directly in the file as a string of characters (or binary data?), so it is not held elsewhere as I previously thought.
I recreated the file, adding screen captures one by one. As I added the eight capture, all the previous images changed to the default icon. When I looked at the raw file, the lines containing the image data had vanished.

So it seems to be a software issue. My guess is that the software can cope with only a certain size of file or a limited number of inline images.
I had no problems when I split out the captures into five separate scrivener files, so this is what I’ll do in future.