The Resolution
Well, I don't know if anyone really cares but here was the resolution (sort of).
I am suspecting the player ('T'), who was actively ignoring the necro-assassin ('V') to help him out, realized he had been metagaming over the week hiatus. Likewise, I believe the DM began to have evil thoughts about splitting up the party somewhat for the upcoming encounter. So ...
T, a powerful cleric type, was already off his horse and looking to investigate. In the previous week, though, he had decided not to. Now, however, as I was preparing to cast a spell (which I found out later would've killed V) he stepped up. I held off the spell since the 'experienced' guy was going to check it out. At this time, I mentioned that, as T had argued the week before, that the Glitterdust's duration had ended. This is when the DM turned evil, and rolled randomly to see just how many rounds had passed. It turned out there were several rounds left. Well, T turns on his true-seeing and, voila, there's V!
To make a long story shorter, V tries a few things, I counter them and then he 'surrenders' to T. I go check out the combat going on (assured by T that he can handle it). By the end of the encounter, T runs up saying "he's getting away!"
Now it seems like we go back into metagaming mode, because no-one wants to chase after him. With me being the 'novice', I capitulate even though I'm positive I can catch him and toast him if necessary.
Now that he's escaped, and I'm calmed down from the excitement of my first 'real' encounter ("Simulator's were never like this!"), I, being a weenie, realize that maybe there's a reason he feels he has to hide. So, what I need to do is neutralize him without killing him.
Right now, my plan is to Detect Creature (V) at some point and then hit him with something like Telekinesis (Combat Maneuver: no save) or Ottiluke's Resilient Sphere (even though I know, metagaming, he has an Ioun Stone).
Any non-lethal/capture suggestions? I cast 6th level Wiz and 4th level Beg spells and pretty much have any spell I want (I've spent alot of money on spells). However, I'm old school (straight PH) so I'm not terribly up on the newer spells.