Did your weight-loss have no other apparent cause, i.e., you had a normal appetite and were eating normally? Or, did the GERD make you nauseous or lose your appetite?
I'm not aware of any studies showing GERD as the cause of weight loss in and of itself. If it causes nausea or appetite loss, then yes, but those are indirect symptoms.
Indrajit -- perhaps we need to know a bit more to answer your questions more specifically. None of the diagnoses you've shared should be behind weight-loss, unless this is an indirect symptom as I described. Also, a 20lb loss for someone who weighs 250lbs is a much different story than someone with a 20lb loss who weighs 130.
I lost weight following my TIF surgery because of the somewhat restricted diet, and my stomach is slightly smaller now, so I get "full" more quickly and don't eat as much. I'm lighter now than I was by a few pounds, but not as a direct result of the GERD.
Other GI conditions can cause weight-loss directly by interfering with food digestion/absorption.