I had the same issue I think. I deleted an image in library accidentally which was background of a section. Then in the section on the left side there was no image field but only image size “large” etc. I removed that size and then the image field was visible again with no image inside as it should be.
It didn’t even show up until now. Before your answer, what I temporarily did was to read in the source code what image name was missing from Bricks (specifically, it was the SEO Social image).
So I created such a file, uploaded it to the Media Library via FTP. From then on, it appeared and I was able to delete the image selection and set a new one with the Trash icon. And I deleted the wrong one from the Media Library.
So it’s resolved and I’ve learned from your answers.