I've read a couple people suggesting that one should always put "Not Found" on a log unless you have first-hand knowledge of the BM being destroyed.
Does that also apply to big BMs? In Pontiac, we have a lot of BMs that are auto-plant water tanks or manufacturing smokestacks. While I could be missing a disc set at ground level, I can feel pretty certain that a 150-foot-tall structure really isn't there.
I thought, given the snow cover, that it would be easier to look for above-ground BMs, but I'm not having much luck. I've found one of five, so far. Two missing smokestacks, one missing water tank and one marker on the wall of a department store that has been gone for 25 years.