The OP needs to do some more research on recording tech. The premise is false.
A recording engineer can listen to the musicians directly and then compare that to the microphone feed (mic, mic preamp, cables, console, power amp and loudspeaker). The engineer doesn't have to speculate or theorize, they can hear if there is any difference.
A recording engineer can listen to the musicians directly and then compare that to the microphone feed (mic, mic preamp, cables, console, power amp and loudspeaker). The engineer doesn't have to speculate or theorize, they can hear if there is any difference.