The new Order of the Stick is up: Giant In the Playground Games.
Neat sudden reversal. I was not expecting that.
This could become interesting. As best as I can recall, destroying the phylactery does not destroy the lich; it only prevents the lich from coming back. Also, if the lich knows it has been destroyed there is nothing in the rules preventing the lich from creating a replacement.
So either Xykon is unaware that his phylactery has been found (and possibly soon destroyed) and is more vulnerable than he realizes, or he is aware it has been found (and destroyed) and creates another, or he is aware it has been found and retrieves it - wiping out most of the resistance in the process when he arrives at their HQ. Any of these paths can have interesting consequences.
A simple Speak with Dead will reveal that the Resistance took the phylactery and if they can scry/track one of the resistance fighters by using an arrow from one of the archers, that would help find it much quicker.
You don't think they'd do it to find out what happened? I didn't think they would ask about the phylactery (how would they know to?) but instead use SwD to help track down the resistance.I'm not so sure any hobgoblin cleric coming upon the battle scene will not just chalk it up to another resistance hit and be done with it after burying/aminating the dead. I don't see any big reason for them to think to ask the dead guys if they had happened to find the amulet before being killed.