I did an experiment last night and found that my OV scanner consistently shows a result which is non-zero after mining an area.
My mining rig is a miner w/ diamond drill, OV scanner (starts will both fully charged), 2x pumps + cells, and I re-fill the pipe after one stack runs out, my base is about 70-75 squares above bedrock. The rig is powered by 1x 32 solar flower.
The first few, I'd mine, backfill with cobblestone and then scan while standing on the cobble and OV scan shows 4-5. I came across one which shows 19 after mining which seems like a lot of missed ore.
I've dug out the cobblestone again with miner and used water to float down and explore the mineshaft, but can't find the ore that I'm seeing on the scan.
Does anyone know what's going on with this? - is it a bug with the scanners, or possibly ore stuck under/around the bedrock which the miner coudln't reach?