By following these steps, you should be able to find and manage blocked numbers on your iPhone.
You can block email addresses (like spam@example.com) in Messages and FaceTime. These do not appear in your Phone block list. You have to check Settings > Messages > Blocked or Settings > FaceTime > Blocked to see them.
Open Settings > Phone > Blocked Contacts right now. Scroll through it. I guarantee you will find at least one number you forgot you blocked.