this post) but this definitely is one, from what I can tell. You can see that this was originally much longer and the tip has been reworked into this shape, probably it broke or wore out and was resharpened into this form. I suppose it still could perhaps have been used as a projectile point but perhaps it was instead used as a perforator or a drill? These points are associated with the period from around 3200 to 2500 years ago. I am happy to have found it. Nearby, Dave found this:
It's really a shame this is broken because it is nice and thin and would have been a monster of a triangle. We looked for another couple of hours but didn't find anything else.