How do I unlock this door with doorknob mechanism/knob off?

I've knocked the doorknob off, other part fell into inside of this closet. I've taken the hinges off the door, but the doorknob mechanism is keeping the door in the frame. What do I need to do to the internal mechanism to get it to release and let me open the door?

(This happened when I was cleaning this closet, noticed someone had stuffed tissue paper in the hole where the knob "latch" goes--because they knew it was an issue, I can only assume--and then it closed for good