Analysis:
I while the above link didn't work, I found the diagrams on the SA website.
What happened? The front surface of the disassembly lever is milled flat when in the closed position. I suppose this is where the base of the guide rod seats, and provides spring pressure to keep the latch closed.
What Andrew appears to have done was push the slide on to the frame with a fair amount of force or velocity. As the lower frame lug hit the vertical surface of the dissasembly lever it had enough oomph to knock the barrel out of its upper lock in the ejection port. I infer there was a great deal of force or velocity used because the barrel came to rest against inside edge of the frame block with enough force to leave those twin dings on the feed ramp.
At this point the barrel is trapped under the slide and being forced down. The front lower lug is trying to push down, but is attempting to occupy the space normally occuppied by the head of the guide rod, crushing it between barrel and frame block. The large longitudinal mark on the rod head is likely from some part of the barrel. Note in the first picture that the guide rod is sticking out in front of the gun much further then normal, because the barrel lug is taking its spot in the frame.
Solution: The gun is now wedged from frame, to guide rod head, to barrel, to slide. Hammering the back of the slide is the most obvious solution, but also serves to put considerable pressure on the guide head. I think the majority of guide rod damage was done driving it off, rather than getting it stuck. Instead, pulling the guide rod forward by its exposed nose while wiggling the barrel may have freed the jam without a hammer. But I wouldn't recommend wedging another gun to find out.
Prevention: Go slow putting the slide on. I can only see the barrel unlocking from the slide with a considerable jar. At a more leisurely pace the slide would have just come to a stop as the barrel lug contacted the closed disassembly latch, just as it does not a Sig or Beretta.
From the engineering side, if the Croates (sp?) were to put a bevel on the upper edge of the latch (in close position) or the lower barrel lug, it would decrease the likelihood of the barrel 'choosing' to bounce down out of lockup. But I would not do this yourself with a file because it could also serve to get the slide stuck in a different, less serious way. But really, a gun shouldn't do this, even with a forcefull tug. A change would be a good idea.
--anyway, he's right on this one.