Good morning,
Your photos are excellent and your encounter is more common than we want to think. You were at the top of your game to notice it was happening and address it then and there. I did a California King that had seams fray in the wash after it was completed. I have slip stitched what I could get to but can not get very close to the 4 corners seams to stitch. I chalked it up as good experience but now I will be on guard as you were.
Regards, Dorothy