Things like that have been done, where someone claims to switch out things, but do not make any changes (so they listen to exactly the same thing twice), and people "hear" the "difference", with the preconceived preferred item naturally sounding "better" when they are told it is playing.
It is funny how so many people imagine themselves to not have human limitations, claiming to have superhuman hearing. If someone claims to be able to jump over a tall building, no one takes that seriously, but when the audio equivalent is claimed, many readily believe.
Humans are subject to the power of suggestion and the placebo effect, and their hearing is not as good as measuring equipment for detecting actual differences, but many imagine that they are supermen, not subject to the limitations of reality.
The moral to the story is to educate yourself, and use your brain, not just your "ears", to make decisions. It will save you money, and you are likely to get better sound and more enjoyment from your gear as well.