Screwed bolt past thread. Now it is stuck. How to remove it?
By getting the bolt positioned in the manner shows in the image, you have effectively filled a hole that is just a bit too tight for easy removal. This means that you should be able to tap with a hammer or mallet the bolt until the thread engages the bar threads. Caution should be exercised to not cause deformation of the bolt thread or bar thread as they near engagement. Consider also to rotate the bolt as you tap downward to assist with the gentle thread coupling.