I think it was touch DNA. (We see BG "sort of spitting" on the video, but I wouldn't bet on it.)
They collected DNA from many Delphi men. Even if they did not sample RA, thinking logically, Indiana was formed by six German families who had relocated from Pennsylvania, so the "founder effect" should be strong, and at least, those descendants could be identified. So, maybe, whoever left touch DNA was either nonlocal, or it was a later NPE case, or just a much later migration.
Or, it could be a very rare Y subclade. Thinking of Indiana Western Europeans: you'd except R1b1b, R1a1a, I1, I2, N1C1, something along these lines. What if it is J, E, G groups? Could still be European, even Western European, but a rare family, arriving much later than the main migration to Indiana happened. If they have full DNA, autosomal analysis can tell a lot, but if it is partial...
I think they hit some common roadblock early enough, some peculiarity, and didn't have full DNA to interpret it correctly.
This is why Paul Holes said, "they have a long road ahead of them." JMO.
RA, I assume, was "local enough." I wouldn't bet on him matching that DNA. I think it is that type of DNA when if you know the ownership, it makes perfect sense, but without it, and especially if it is partial, it should indeed look peculiar. I wonder if they looked at the Interpol samples, not because I think this DNA is there (I am positive it is not), but just to see who could have a similar pattern. JMO.