>>1839947>how to get it out?If the wedge actually fell down then it's not holding the stem in anymore. You can remove the stem. Then remove the wedge.
If it is still there, you need to re-thread the bolt back in some and then knock it down, to release the stem. Make sure the bolt has a reasonable purchase or you will damage the threads.
Lubricant will not help if the body of the stem is actually badly stuck because it will not penetrate the corrosion.