Comment 57 for bug 1254884

Unmuting via pulseaudio works fine, so whatever does the unmuting when you press the mute button on your laptop is, with very very high probability, not using pulseaudio.

I had a look at xfce4-volumed code, and it seems to rely on GstMixer. xfce4-volumed doesn't seem to care about the mixer implementation, it will just use the first mixer implementation that it finds. That might very well be an implementation based on alsa, not pulseaudio.