How to Undo Stupid ??

[keithhe]

Well, and I thought I knew better, but in my haste to make a quick change to a plan I manged to use the material painter and screwed things up.

Didn't see the problem until I was trying a Ray Trace, so too far gone for an undo. I noted that screens were solid in ray trace, so knew I had an issue. Problem is the inside of a pony wall defined as lower stucco outside, bead board inside and upper screen. Looked normal from outside, so didn't catch it, but from inside all suraces are stucco, to include the screen. The DBX is correctly showing what it should be, so how does one undo this?

Really stupid and I know better, seriously, just one area of a not connected wall. I'm really embaraased by the rookie questions I have to post here..........