Given that feelings cannot not be physically detected, then it is 'logically possible' that some people have none. I regret to say that almost every student confronted with this can find no good reason to dissent. Obviously that is logically possible. Although it seems implausible, there's no way that it could be disproved. But again, that's just what we were trying to prove.
Experience is all or none.
You either have it or you don't-and there can't be anything in between. One is that it appears to be elementary and irreducible-as seemed Gravity before Einstein found his new way to look at it. The opposite case is when the 'thing' is so much more complicated than you imagine it is, that you just don't see any way to begin to describe it. This, I maintain, is why consciousness seems so mysterious. It is not that there's one basic and inexplicable essence there.