yes

Divers wearing headphones? Regardless, I suspect that after a million years there won’t be much left of the headphones.

Of archeologists don’t know it: “for religious reasons”.

I think headphones aren’t tight enough to leave divots, but cochlear implants might make them wonder.

1. If the civilization that discovers it is more advanced than 20th century humanity, then no. They would know their purpose.
2. If it’s not as technologically advanced, the it’s possible I suppose