If it's really jammed in there I can't see it coming out. How hard are those things? If it's the least bit soft I guess you could try stabbing it with a fish hook and pulling. A tiny drillbit might be able to grab it. I'd probably start with a needle.
Those jacks aren't like the generic ones from the old days. On those the jack is open on the back and you could push something like that on through. The MBP's are closed inside:
I did try a hoover, however after I tried inserting the headphone plug, (which is when I discovered the ball in there), I think it pushed it in tight. I did remove it by scraping with a sharp jewellers screwdriver.