The disconnect wouldn't be holding the slide up. You should still try to manually move down the sear release though. That's a different lever than the mag disconnect. Pulling the trigger should release the sear though, although you still may want to manually move that lever just to see if it makes any difference.
I suppose it's possible that the recoil spring and guide slipped out of their little groove/channel on the bottem of the barrel. That's why I wondered whether you could put it back together and cycle the slide. If you can do that, you'll know the spring and guide are in the proper place on the barrel. If you can't get the slide back on all the way to cycle the gun, your spring/guide rod may have dropped down off the barrel and be hanging up inside the gun.
Only other thing I could recommend would be to pull the magazine, pull the slide back so it's latched on the slide catch lever, use a tool or your fingernail to reach into the breech and move the sear lever down, move the removal lever straight down, turn the gun upside down so the top of the slide is pointing downward and gently pull the slide back to release the slide catch, walk the slide off the frame rails with the gun inverted.
Boy, do I feel stupid. 
