No Sound from known-good external speaker, after coffer spill

Coffee cup turned over. Beverage meandered over to cell lying on the table.

Dried it, then made an amateur mistake; tried to call friend's cell. Buzzing. Hung up, put cell in my pocket, whence it commenced with a vigorous buzzing sound. Removed cell from pocket and powered down.

Took it to tech who instructed the rice maneuver.

Several days; no sound from external speaker.

Samsung sent it back to me - not a manufacturer's defect.

Neglected to mention that I'd previously swapped-out external speaker module with new one which I'd purchased through Amazon.

Question, now: What circuitry do I need to look at/swap-out ?