You might have starved to death, been in your last stages of poison, suffocated in a block you placed, stepped in a fire, got shot by a skeleton who was just far enough away to avoid your notice, stepped down off of something that was a tiny bit to high, or a host of other things. Able staff almost never use /kill unless it is needed and you would have received several messages from them before one would use it. There are so many reasons you could have died. Consider what exactly was going on. Also in your log it may say if you died at the hands of a hidden player or one hiding just out of sight.
