DH - It's an interesting question. I think out of manners just loading up a box or rocks feels like taking something that doesn't belong to you. But, periodically the pit has to be cleaned out and loads of useful stuff goes to a dump pile, where it can be picked through. When people are sitting there knapping... the stuff on the ground is fair game when its been sitting there and the person who left it isn't claiming it.
It's kinda funny you ask that question, I've never really stopped to consider the etiquette behind the debris.
If you were to go to Mullet's place or mine, just grabbing something would be wrong, of course. But, at Twin Oaks it is a club and it belongs to them and Pappy. It seems the best thing to do would be to speak with Pap. Hospitality and generosity are valued highly with those folks. That's my 2 cents.
Do you intend to go to The Classic next spring? Or, another event?