Missed call on my iPhone at 2:05 AM. No message left. Number is not in my iCloud Contacts list.

I put the number into the "Spam" entity in my Contacts. All incoming calls to numbers included in my "Spam" entity trigger a "silent" ring tone and "no vibrate", so I am not bothered by them. If anybody with a number in my "Spam" entity truly needs to talk to me they can leave a message and identify themselves.