Okay, as a jaded veteran of running security for many, many events, parties, and conventions when I worked for the casinos (along with my other duties there) my basic attitude is that this is an unverified, and basically unprovable story, as such it deserves absolutly zero attention. To be honest the kind of paranoia over bad publicity that inspires someone like Notch to take a fairly personal interest is exactly why people tell stories like this, despite their claims "oh, I didn't want the attention". To be honest not wanting to make a scene or whatever tends to be the first refuge of a liar in cases like this. I also tend to notice qualifying statements about "maybe" having invited the behavior "accidently" of course, which typically means "yeah I invited it, but now I want to make a complaint and get some attention".
The bottom line is that as security your job is to keep things quiet and prevent *major* incidents. What happened here at the very worst is gross and all, but unless the suspect is clearly pointed out, and we have some kind of proof, or a pattern of behavior, security isn't going to do much more but keep a subtle eye on the guy and watch out for more complaints. After all the surest way to screw things up is to ruin everyone's fun by making a scene, especially if it turns out the accusations aren't true. In some cases if you have a camera on the scene you might rewind a tape at some point to find out the truth of the matter, but it depends on the exact circumstances.
Sure you can say "OMG, the guy could be a sex offender, he could be building up to throwing someone down and raping them in a stairwell or something", sure, but then again your dealing with a party with rowdy kids and drinking, where people routinely cop a feel and even invite it. Sure you have incidents where people get unwelcome attention, but hey, that's parties.
Understand that the bottom line is that it's a he said/she said incident of a relatively minor nature for the situation as described, where in the absolute worst case scenario the victim claims she might have sent the wrong signals and invited it. There is no proof of any sort in either direction, and as odd as it might sound you can't start doing backflips every time you get a verbal complaint like this.
From the sound of things Security probably handled it well for the setting given the actual information present here, nobody was harmed, and there wasn't a big scene since this apparently wasn't even known by most until after the party which meant security kept
things quiet and orderly. Notch is probably creating a bigger problem than there actually was by expressing outrage over something that might not have even happened.
To be blunt if Notch wants to cut down on the rowdiness and the possibility of things like this happening, the first step is to not serve or permit alcohol at his parties. From long experience, the moore freely the booze flows, the more likely your going to have crap like this going on.
I'll also say that if you want to see people "bounced" purely on verbal sayso of other patrons, it won't keep order, you'll see people trying to get other people bounced for lulz constantly, which is why most places renting space for events might let you pay to use their security, but they won't let you hire bouncers or usually bring your own security people in (though like everything, there are exceptions). Assuming Notch's security worked for the hotel (or wherever this was happening) it seems like it was handled well given the circumstances, if these guys were convention security that don't even have the protection of "acting as a representitive of the property owner", no sh@t they aren't liable to do anything, they don't even have the most tenative actual authority to do anything in a
case like that no matter what they might think (and yes, I've dealt with things like that before, even going so far as to have volunteer "convention security" walked off property by way of making a point, and to avoid any confusion about authority. It was years ago but once we had some guys from Agway get uppity on similar matters, it didn't happen again).
