When you click on one of the relic weapons to loot it, the confirmation screen comes up to confirm you want to loot something that will bind to you. If you move, or miss click the OK button the Weapon disappears and will never spawn for that character again.
You still get the XP and the Achievement credit but no item. I have put in a ticket as I had this happen multiple times. GM said they could not do anything because on their end it didnt show me looting it.