Hi KC,
Ummmm. I don't think you want to drive that out with the slide lock inside the slide. It would at the least damage the slide lock half moon area, and could bend/gouge the slide.
First thought I can come up with... maybe it's caught on the cocking cam??? I don't have a P380 to look at, but looking at my CM9 I think you have the gotten the feed ramp pushed up against the slide stop pin and the cocking cam is behind the slide cover plate.
Try pulling the trigger and turning the gun upside down, and jiggling the slide, pushing forward trying to slide it off again????
Don't force anything yet. But maybe a gentle bump with your palm to the back of the slide while doing the above????