If you're curious to learn more about what a collapsed vein is and how it happens, I found an article that goes into detail about it. It explains the symptoms and the causes of vein collapse, which might help you understand your situation better
https://unitedrecoveryproject.com/rehab-blog/what-is-a-collapsed-vein/ . It’s worth reading if you want to know more about how veins can get damaged from procedures or other causes.