After some tests I find this:
1. If you have a missed call and your first move is to open the notification center you can see the missed call on the All tab and from the All tab you can erase it and then erase it automatically also from the Missed tab.
2. If you have a missed call and your first move is to unlock your iphone to see the missed call from the phone then the missed call is appear only on Missed tab on the notification center and you can't delete it! The only way is to reboot or to wait for 24 hours.
All this happens on my iphone 5S. On the iphone 4 and iphone 5 that I checked this issue it seems to work normally... In all cases the missed call appear also on the All tab on the notification center and you can delete it any time you want.