I had child's bike in the shop on which the wedge was corroded and frozen inside the steering tube. In this case the stem was aluminum (the wedge was steel) and I did manage to get the stem out with the wedge still frozen solidly in place. I ended up using PB blaster, the original long bolt and my slide hammer to pull the wedge out after repeated attempts to drive it down failed. In this case, being a child's bike, I suppose the wedge may have been bottomed out with nowhere to go despite the hammer blows.