I had the same experience as dude in that my phone didn't ring or it rang and was hung up. I have a missing call that I didn't even hear come in because I was listening to music player on my phone so that's improbable. Although, I've never spent a week in the Denver area.
It has been awhile since this number called me but it has happened before when I answer it is dead and I don't hear a click from them hanging up. I would like to annoy them back.
I was on another call when this number came up on called ID. When I clicked over, there was just dial tone. I tried calling the number back and the call wouldn't go through. I tried from my landline and got the same. Basically, my experience was the same as others who posted here. I just hope that it's not a repeat annoyance as others have reported. There's an option on my phone to block specific numbers. After reading these posts, I believe I will take advantage of that option. Am grateful to all who shared their experience(s). Thank you.