I'm having this same issue.
All locations empty. Missing 1 Doom spy bot and 1 Silver coin. GRRR played every level so many times.
Found my last coin in the Lincoln tunnel (Swear it wasn't in pants' guide)
Still no dice on the doom bot I've searched all locations multiple times.
EDIT:: Alright I found it on the stupid Terrax 2 some how I knew it was there but I kept searching the first pressure plate room instead of the second.