Another vote for removing it rather than running the risk of worse trouble later.
If it is still in the dipstick tube, I'd try to fish it out from there. All of the methods suggested would be worth trying. I might also try fine welding wire with a small hook turned in the bottom end.
If it's in the sump I'd be tryin gto fish it out through the drain hole before I tried to remove the sump. (If removing it is difficult, think about getting it back on!)
Best of luck! Let us know how you get on.