> ask steam friends to go onto the server and spy for you, preferably while on a skype call
> check chat logs
> check your ban list, see the reasons and time given, would you do the same?
> host a dedi, ctrl + k, use console to "leave" the server. Say nothing, do nothing. spy. (unsure if this is possible, but I've seen console do some weird stuff, so I wouldn't be surprised if it was possible to remove your name from playerlist and then just make the chat say you left)
> de-admin them all. The ones that beg for admin don't deserve admin. The ones that ask why they were de-admined are worth considering. It shows they are at least concerned with their actions.
Just use common sense. I have admins who have worked with me for coming up on 4 years, and then I have admins like Furdle who I have to keep an eye on, otherwise when I come back half my server will be banned. Don't admin strangers, admin people you know. All of my Super Admins have my email, facebook, cellphone number... We carry eachother. My admins are just people I know in-game and trust.