How do you get mithral plate?

In Dorn's Deep where you should get the Mithral Plate +2, where is it and how do you get it? It went to the room with three furnaces and i didnt see it, or see door on furnace, or a normal way to open furnace. Is the plate on one of the drow, i didn't check all of them, just the archers. I have waited too long and all the items have since disappeared, so i hope it wasn't on one of them. Thanks in advance for any help.

I think the mithril plate +2 is in a pile in front of the drow who are way over on the top right of the map. This is the same map that has the huge fight when you enter, with archers and mages on both sides of a bridge you cross.

I suppose if you didn't fully explore the map, you could miss this pile and the three drow guarding it. You can also get a good crossbow or two and some Bolts of Biting off the drow there.

This really surprises me because although i missed my chance to get it, not long after i started playing Icewind Dale again i found the damn plate in the shrine in the frost giants cavern, is there one there always, or does the game make sure you find certain items?

The game doesn't make sure you find the items they are there if you want them. The mithral plate is good but the Bathed in blood armor is better, you can find that in the thives guild Marketh's Palace his body guards have it-

[Shadowblade]

I have played through the game 4 times now, and I have always gotten 2 sets of mithril plate, one in the frost giant cave in a secret hole hehind Frostbyte and the wyverns,and the other in the upper Dorns deep by the forge where all the huge giant sized weapons are, u have to kill a drow sorcerer and 2 drow vanguards though, and there in a pile with the Axe of Caged souls infront of the forge.