There's a theory[0] that the bloke from "Into the Wild" died from seeds that weren't in his fieldbook because they had never been known to be poisonous at the time. Again, though, I agree - pack your own food into the campsite.

[0]https://en.wikipedia.org/wiki/Chris_McCandless#Swainsonine_i...

This is the only way. It is a tautology, but a plant is only safe to eat if you know it is safe to eat and can identify it correctly.