You wake up in your apartment, as everything seems like normal at first. You think that it's likely that voice was just a dream, with both your room and the city outside your window looking like they always did.
As you sit up you can feel something hard within your pants. Like some sort of tense muscle sticking out of your crotch area. You begin to frantically realize what this may be.
Looking down you see that you have a small tent in your pants. Unmistakably created by an erect penis. You realize you can feel smoothness where you vagina once was. Your new anatomy feeling so alien.
Opening up your phone and quickly searching "female anatomy" you can find to your shock that there doesn't seem to be any concept of a vagina. You've now woken up in a world where everyone has male parts downstairs. Including yourself.