Others have already brought up this point (here or elsewhere), so why are you ignoring it for your cosmic example? The drive itself will know what data is wrong since the hardware supports checksums of sectors, so if a data bit is flipped and it doesn't change the checksum information, the drive will report it.
In addition to that, you may know what's wrong if the filesystem used supports checksums or you use a 3rd party plugin for checksums.
Mathematically it is impossible to know which disk is wrong with the algorithms used by single and dual parity protections.