It's unfortunate this case has passed three decades with no resolve, and a greater disservice that no local media outlets have touched base on it. I took a quick peak at the zine "Berkeleyside" (the symbolic successor of "Berkeley Voice"), and just like my second post here suggested, regional interest is still more aligned to niche political topics than non-partisan, genuinely humanistic issues like missing persons.
I still stand 100% firm that a Tilden Park fall accident was behind Peter McColl's disappearance, and the secretive urgency behind his trip was concern over the sedentary effects of his arm injury. Specifically, he either took a deliberate off-path hike, or attempted a shortcut from one trail to another, which ended with a fatal descent down a cave, glen, sinkhole, or sinking stream (which are common all over the East Bay hills).
Another supporting clue (which hasn't been brought up anywhere) was his choice of dress that morning: a sweatshirt advertising his HS sports team. While not entirely definitive, this tends to be the attire of choice for someone either a.) attending a game, or b.) training for their own (or working out while showing spirit). Temperatures that day were mild enough for such a garment, per historical weather data. As far as Doc Martens - not the most ideal boot for a hike or jog, but they were fashionably en vogue during the 1990s and still worn by energetic individuals.
The roadmap for any other lead/theory is extremely limited. In the Bay Area, there were no pattern-kidnapping cases or serial killers loose at that time; no jailhouse confessions; no evidence the teen associated with bad actors (or dabbled in nefarious activity). Suicide or drugs would be credible if there was evidence he was experiencing a downward spiral in his life. But everything presented illustrates a bright (albeit freethinking) individual with a zest for wanderlust and a penchant for his rowing team. And it was the latter passions, IMHO, which inadvertently resulted in tragedy.
