It's probably not simply glued; it will have solder tags that go through the board to be soldered the other side. For any decent tech, it's an easy fix, and all the easier if it's already out of the cab, so it may be worth popping into your local secret underground electronics lab and asking nicely if someone could operate on the poor thing. At worst, the 'switched' part of the socket could be shorted out, so that the speaker is always 'on', and another, in-line switch fitted to the speaker wires (one similar to those fitted to bedside lamps or similar...), so that it may be muted when using cans. Just a thought.
Douglas