I think you're misunderstanding what he was saying - he said he went through the door without killing the slig so when he came back the slig was still there. And when you're on that side of the screen it's impossible to run back to the left screen before you get shot.
One thing I'm curious about is, how did you manage to get through the door in the first place without being shot? I don't think I've ever done it before. I vaguely remember something like this happening to me once, but I think that may have been something to do with using a certain TAB button
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I'LL GET MAH STABBIN KNIFE!
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