ahh... well, I don't know what .vol it's in exactly so I can't tell you that, but, you won't find it in any .mis file.
Your best best is unvoling every single .vol that has buildings in it, each into their own folders, and then put them in one at a time to your rpg directory until you find it out. This will work... but it's damn tedious...!
Once you figure it out, make a folder in the directory it's supposed to be in called keep_old and a folder called keep_new. Put a copy of the old rpgmap 1 keep into the old dir and the 5.005 into the new. That's just to prevent this fiasco from happening again... and to let you switch them if you feel like it ;-)
//sleep!