I don't believe screaming/yelling could be easily heard. There are variables, of course. If it had been summer, the trail would likely have at least some traffic mid-day. And while sound can carry further at this time of year (no leaves on trees), the homesteads are large and somewhat distant from the bridge. Also, the noise of the cars/trucks traveling on the highway that runs near there would compete with any voice carry (if you google it, you'll even see two semi trucks passing over Deer Creek on 25, which is probably less than a half mile from the bridge. So no, I really don't believe cries for help would have been easily heard.
I have to say, after hiking in Delphi, the "vibe" made me suggest to my dh that we consider carrying for our own safety (we can conceal/carry in IN). We encountered an intoxicated older man on the trails, along with a pot belly pig (yep, running at us from a distance; had our kids with us and couldn't make out what it was at first).