Front wheel hit and bent cvc axle

First of all, the half shaft is the last thing that should get bent from hitting a curb. The most likely part would be the wheel.

For the half shaft to come out of the transmission, one of three things would have to happen. There could still be a bent control arm that is causing the wheel to sit out too far. That would pull the half shaft out with it. The problem with that is you would almost certainly notice a severe handling problem. The second thing is the engine mount that positions the engine could be off-center to one side, but that is not likely to occur from hitting a curb. It is usually the result of improper installation when it needs to be replaced or when it was loosened to perform some other service. The third and most likely cause is a broken spring inside the inner cv joint, especially if it took part of the impact. That damage will not be visible to the mechanic, but that spring is what pushes the inner cv joint housing into the transmission and keeps it there. I've replaced those springs on a few Chrysler vehicles in the mid '90s. They just caused a minor shimmy, not complete disengagement. Those springs cost $3.00 at that time and took about an hour to replace. To find if the spring is broken, your mechanic will try to push and pull the cv joint housing on the shaft. It should take a lot of force to compress that spring and make the housing move. If the housing moves back and forth about three inches freely, that spring is broken.