Just found a 2017 study that looks at pepsin-in-saliva detection as an alternative to endoscopic examination. Promising but still preliminary. But you probably already knew this...
The diagnostic value of pepsin detection in saliva for gastro-esophageal reflux disease: a preliminary study from China
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5645897/
But what I found in the discussion supports what I said above about how the pepsin in your throat causing LPR to develop is due to gastic reflux that isn’t severe enough to cause heartburn symptoms (GERD). And there is even a medical term for it: non-erosive reflux disease (NERD) — and is more common than heartburn.
Recent studies showed that the PPI test and structured questionnaires did not obtain ideal sensitivity and specificity for diagnosis of GERD [4–6]. Endoscopy is not adequate since [b]non-erosive reflux disease (NERD) is more prevalent than erosive reflux disease in the GERD population[:b] [7]
Bottom line: You definitely have had, and likely still have,
some amount of gastric reflux to cause the pepsin to be present in your throat, precipitating the LPR, but not severe enough to cause erosive damage to the bottom of your esophagus.