Lesson learned the hard way, I killed one GPU today by mistake, I was supposed to use riser the right way but I turned it the other way, I was not in my right state of mind because of what happened at home( family issue ) so now the GPU seems dead, no display and fan is just running slow.
did it arc,spark,shut the rig down?
it may still mine on a rig with a few cards.
did you toss the riser?
if you are lucky the riser took the hit not the gpu.
try a different riser.
i did something like you did and killed a mobo board slot but the gpu worked in other slots.