Hi evilscamp..
1) Make sure the audio is coming out of the PC. Hook up any speaker/headphone that is known working to PC. If sound present then trouble is definitely monitor.
2) If monitor has volume control or setting in the OSD (On Screen Display) menus, ensure it is on, and volume level is up (said you did this)
3) If no sound then problem is LCD.
a) If there is no volume control, then the speaker volume is dictated by the PC, and the speakers are simply wired to the female 3/8" jack. Unlikely that they all broke off, but if LCD female audio plug is loose, or rotates freely this is possible. Only solution is to open LCD (voiding any warranty) and find/solder the connector.
b) If there is a volume control on LCD, then problem is probably the little pre-amp inside the LCD. If it is fried, it may be difficult (if not impossible) to find the correct replacement part. If LCD is on warranty - get an RMA and send it out. If not, the only solution is to either buy small desktop speaker set, or open LCD (again voiding any warranty) and soldering the 3/8" female plug directly to the speakers(bypassing the preamp) and using the PC to control volume.
Grant