That incident you described to us in that last post of yours, is undoubtedly freakish in nature, but commonly exists in places you can't see or may not be familiar with or have no reference point to go from. Most will say that they walk and inspect the work area, many do not, personally I don't stray off the land here, and know where things are, but if working in new places, I would have to see it off season, early spring, late fall, clear/mark/note hazards. Not going to be the cure-all but most likely time well spent.
Things like that pipe are just incredible in how they find an opening and just rise up to impale you. I've cleared quite a bit of brush and trees in the past, lots of it on dozers, but here at home, just my old tractor and mower. Fortunately for me no injuries, but I can't say how many times, I've raised one side up on a stump or log, been smacked by something under tension etc. My old tractor has a loader with lines to catch on things, I won't brag, but with all I did with it, only 1 time did I pull the return line to reservoir off. I can see a few small shallow slices in my tires though, not good at today's prices ! One incident on my D7 caterpillar, is still vivid in my memory though, this is an open station, no rops tractor. I cut with a chainsaw and rough cleared a small area to connect to a field next to my house, down a slope. Next move was to bring the crawler through, don't you know seemingly out of nowhere a limb or log hits me in the side of the head! Tough ole melon up there, however it almost cleared me off the seat not to mention its effects after. To this day I don't know what I missed, but it was something up on the left embankment, could have been a vine that caught because my tracks were clear blade was up and plenty of room. This stuff comes from out of nowhere sometimes with no time to react, and like you said, who is going to find or help you, good to hear you did not get hurt, getting impaled in the abdomen by a blunt steel pipe is something hard to imagine. A neighbor over the hill, was mowing in rough terrain, he got tossed out of the seat of a 640 Ford, went under the rear tire an through the rotary cutter, an ugly scene, was found hours afterward by his brother.
In all, I have learned to respect all work areas regardless!