I engaged a Gorn on a cliff and took him out for an uncommon reward... and then I could only stare at it since there was no way to get to the reward.
Think about that one devs.
There's plenty of Gorn at ground level in the canyon giving rewards that players don't have to fret over missing the half dozen Gorn on the cliffs that may or may not drop a reward that can't be reached.
Furthermore you can dawdle in that canyon for as long as you like because the mobs respawn. I filled and recycled my inventory three times and before I grew tired and went on and finished the mission.
Don't be greedy about the stuff dropping out of reach, get over it and move on.