My cape Founder's cape disappeared and never returned to my account!

I've had this account for years, and it contained the founder's cape. In a certain version (which I don't remember), it disappeared and never reappeared. I recently saw rumors that this was a bug and that it had returned to all accounts, but not to mine. I tried everything to find the link that redirected to the Steve and Alex skin pack on the marketplace to retrieve the cape, but it gave an error when opening the marketplace in Minecraft. Below is an image of my capes and then an image of the error that occurs when trying to enter the link:

I'm just a collector, and I just want my cape back, that's all.