As you mention you do on occasion experience acid reflux, a consideration of your symptoms could be related due to irritation and inflammation of your esophagus (esophagitis), from stomach acid into your esophagus which can lead to inflammation and a sore throat.
If left untreated for long periods, acid reflux can cause:
- Esophageal narrowing (stricture). Strictures occur in some people with GERD. Damage to cells in the lower esophagus from acid exposure leads to formation of scar tissue. The scar tissue narrows the food pathway, causing large chunks of food to get caught up in the narrowing, and can interfere with swallowing.
- Esophageal ulcer. Stomach acid can severely erode tissues in the esophagus, causing an open sore to form. The esophageal ulcer may bleed, cause pain and make swallowing difficult.
As you have stated you have not had heartburn in the past, depending on how severe it was this could be something to consider.
My feeling is that you may simply have a viral infection which can cause a sore throat, in view of the fact you no longer have your tonsils or adenoids. A sore throat that lasts longer than a few days should really be evaluated by your doctor.
I have provided you with the most common causes of a sore throat. As you would agree, without me being able to examine your throat, I can not tell you exactly what your diagnosis is.
Lastlly, another consideration is do you suffer from seasonal allergies which cause a post-nasal drip? If so the constant dripping from the sinuses into the back of the throat can also result in an irritation that causes a sore throat.