I went back and re-read this entire thread in search of how the "substance" discussion began, but I don't see anyone else talking about substances - or "hits," for that matter - besides you. Please direct me to a post where another poster refers to those specific words, or to an article that uses either of those words. I do appreciate you laying out your line of reasoning, though. One could plausibly make a case for reading between the lines to arrive at the conclusion that they found some sort of bodily fluids, BUT...
...I hate to do this again, but the original, written-in-Spanish article, uses the word "rastros." Google translates this word to "traces" in the article. BUT WAIT! "Rastros" can also be translated "trails," "tracks," "signs," as well as a couple other words that don't fit in this context (e.g., rakes). Those alternatives, IMO, lend an entirely different slant to "traces" in my interpretation. E.g., not so much "trace amounts," but visible physical markings of some kind ("Tracks," like as in prints from his walking boots, make the most sense to me considering the greater context, but MOO)
And all kinds of things can be analyzed in a lab - objects, substances, footprints, etc. etc.
Look, I am completely neutral on whether they have found bodily fluids, personal belongings, footprints, hair clippings, teeth, drawings in the sand, whatever. I don't know what they have found. My knowing what they have found is not important.
But IMO, it is a big stretch to use a robot-translated text to hunt for clues. Websleuthers are not going to find Prof Marsh by divining what sort of evidence the Chilean investigators have discovered, and I hope that we've been able to see some of the difficulties that arise when translating text from one language into another. I'd just like the discussion to stay on track in reference to known facts as they have been reported in the original language so that it doesn't turn into a game of telephone, as evidenced by "the chair" situation from earlier.
All MSO (My Soapbox Opinion, can we maybe make this a thing? A new acronym?).