I don't think the Order's ambush was completely negated. It seems to me that a lot of posters have forgotten the Order was retreating from an ambush by the LG. At that time, the Order was outnumbered and outgunned, so Roy gave the order to retreat. Down in the depths of the pyramid, the Order pulls off an ambush of a superior force. The LG has been weakened to the point that they have to flee, or risk destruction. Now the Order has the time to heal, locate V, and to locate the Gate (if possible).

Besides, Tarquin is a high level adventurer who has almost certainly been around since 1st edition (Haley's father also started out as a 1st edition character). He should have lots of practical tricks and abilities learned over the decades. What good high level adventurer wouldn't? I also think that Tarquin has been defeated a lot, and has learned from those defeats.

I also think it likely that Tarquin has more than one powerful weapon available. The loss of the axe will hurt, but he can go back to his personal arsenal and get a new weapon. Most high level PCs I've known have more weapons than they can carry around. And it is always good to carry a light weapon (like a dagger) for those times that light weapons are the only ones useable.