Had a miscarriage and didn't even know I was pregnant

So basically I've been reading bout miscarriages and 2 years ago I had the exact same symptoms as a miscarriage at 5 weeks. I had missed my period then a few weeks after I had a wide and long tissue in my knickers with a lot of blood I was younger so I thought it was just a blood clot but what was weird it was really long and really wide and it was white but covered in blood I still can't believe it