Stuck AR bolt

A coworker presented me with a dilemma today. He was boresighting his AR and managed to let the bolt slam home on the chambered boresight device. He called me to ask what to do and I told him to collapse the buttstock and bang the butt on the floor while pulling hard on the charging handle. He said it won't work. I told him the I had always been able to remove stuck rounds that way with no issues. He said that he had separated the upper and lower, and tried to pull the bolt to the rear. It came back a short distance and stuck. Wouldn't go either way. He reported that the bolt locking lugs were not rotated into the locked position, so that it should come open.

He's bringing it to me tomorrow for a look-see, but meanwhile I'm puzzled. I took one of mine apart to visualize what he was describing and cannot understand what may be holding the bolt closed. What would be holding the bolt such that the bolt carrier could not be pushed in enough for the upper to be closed on the lower? Are those boresighters made to the same dimensions as the cartridge? If so, I would think that it should pop out.

Well I got it in hand and it is stuck pretty hard. The bolt carrier will not fully seat (which would allow the upper to be closed on the lower) nor will it retract more than about 1/2". The bolt is not locked. The lugs are not turned into the barrel extension. The firing pin is still in place. I'm thinking a slide hammer type rig with an L shaped extension to hook into the back of the carrier would probably get it out. Got a little fab work ahead unless someone else has a better idea.

Just to follow up - I got the bolt carrier group out with a fabricated tool made from an 8" long bolt. I ground part of the head off to make an L-shaped hook that would slip into the carrier and engage the full diameter portion at the back of the carrier. Thankfully it was not one of the Colt carriers with to bottom cut completely off. The bolt is softer than the carrier so any hammering would mark the bolt and not the carrier. Installed a nut and washer on the other end to grab the vise and yanked on the upper like a slide hammer. The back of the boresighter came out leaving most of it in the chamber. That was still stuck hard, so I soaked it down with Kroil and let it sit a couple days. A brass rod got it out with a few firm taps. Close examination shows no damage to the bore or chamber.