OK, sorry I didn't expose my doubts properly, I'll try to explain myself as thoroughly as I can: What I learnt is that SMART performs "offline scans" (that's what Wikipedia says to name one source) and keeps a log of bad sectors found. So it's not strange to imagine that those scans are intended to detect bad sectors on the surface of the drive (meaning on the platters of the hard drive, where else?), thereby my doubt. My idea is that perhaps the bad sectors are only detected by SMART when they're used (read or written), and therefore, if there's a big chunk of the hard drive that hasn't been read/written for a long time and there were bad sectors in that area (due to a head crash on that area that would produce hard bad sectors or to a mismatch between the info in the sectors and the EEC, which would produce the so called soft bad sectors), they wouldn't be logged by SMART until those sectors where used some day in the future or if you use some utility that scans the whole surface of the drive or simply if you zero all the hard drive sectors or perform a full erase. But I'm not sure, thus my doubt: does the offline scan look for bad sectors? does it perform a scan of the whole surface?
Thanks anyway.