Postpartum bleeding

I'm two weeks two days postpartum. My little guy woke up to eat and when I got up to feed him I felt myself pass a huge clot. Thankfully my mom is here helping out so she took my baby for me so i could go use the bathroom. The clot was the size of my entire open hand, it basically filled my entire pad. I messaged my sis who is a l&d nurse. She told me to wait an hour and see if I filled another pad. I had hardly any bleeding after that so she says I could just wait and call my OB when they open, unless something changes before then.

Anyway my question is, has anybody else had this happen to them? I'm guessing it had to be part of my placenta??