[sejje]

The information is lost in the sense that it's in the original, and not in the lossy version.

Whether or not you can hear it, the information is gone.

[mdisraeli]

If you can't hear it, was it ever information?

[daeken]

We can't see in infrared, but there's clearly information there. Same with infra/ultrasound and other sounds that are buried in our hearing.

It may not be pertinent information in the case of music, but it's definitely information.

[sejje]

If you cover your eyes and can't see me, do I still exist?

[TheOtherHobbes]

MP3 is audibly lossy, especially at lower sample rates.

So yes - you can hear it's gone.

And if you look at a spectrograph, you can see it's gone, too.