Not unfair comments.
Our OP began this thought stream with:
I unclipped my left foot and put it down to stand and then went to unclip my right when I saw traffic would be a while. Next thing I know I'm on the ground with my right foot still stuck in the pedal.
Got pretty bruised up. The idea that a trike can't fall over has more appeal than it used to.
So far suggestions have included recumbent trikes and crank forward bikes, with associated positives and negatives. Any other suggestions for the 50++ group, whose balance & flexibility maybe isn't what it used to be and who are perhaps more wary of injury?