grumble!
I've been growing a Robinia Pseudoacacia from seed for the last 20ish years, trained into a nice looking bonsai about 4 feet tall, just on the edge of being a 2-hand size. I've been progressively carving the trunk to turn it into an old-looking rugged thing. It came out in leaf early this year, even looked like flowering.
Then all the leaves started to die back, I'm not sure if it got hit by the late frost or not, but I don't think it's fully hardy in that respect - OK over winter, but not once in leaf. Anyway, I gave it a trim last week, there's some green below the bark, but it's not looking like sprouting at the moment. This was one of my favourites as well.