Well, I'm really confused and more than a little embarassed now. You'd written first that a gunsmith had taken the gun apart. I never would have thought that a gunsmith would not know how (or at least be able to look up how) to remove the barrel in taking down this pistol. "guess kto", you're the really bright guy here. I felt sure the barrel was the problem, but I never thought no one knew how to take it off.
Just to make sure that the solution to the problem was in fact simple fieldstripping of the gun, below are step-by-step instructions on a quick way to take the slide off the frame without actually taking everything apart, just to make sure that's the solution to your problem.
Pull back the slide so you can push the take-down/safety lever into the forward recess on the left side of the slide of the pistol. Then you can turn the barrel a quarter-turn. Once that's done, depress the safety/take-down lever and keep hold of the slide. The slide/barrel assembly should be pushed (not with great force, but still under spring pressure) off the front of the frame by the pressure of the compressed recoil spring. When the slide comes off the recoil spring will remain in its socket in the frame and you'll know the answer to the problem.
A note of caution. With the slide off the frame, the automatic hold-open on the right side of the gun can fall off the frame if you're not careful. Since its also the trigger pin, you don't want that to happen. Just keep an eye on it. If it does fall, just don't move the trigger. You should be able to slip it back into place without trouble.
Then you can simply slide the slide back onto the frame (making sure you don't bend or kink the recoil spring) just the same way it came off, hold it in place with the safety/take-down lever in the forward recess, rotate the barrel back into position, and depress the lever to allow the slide to return to its "normal" closed position.
You'll need to consult the takedown instructions for further disassembly. I can help with that if you wish.
I'm really sorry that I never considered that the gunsmith didn't know how to fieldstrip the pistol. I believe "guess kto" is right and this will solve your problem. Congratulations to you and "guess kto" for figuring it out. Have fun with it.