I would do whatever it takes to get it out ...
Obviously, the easiest things to try are the simple ones (fishing around with a wire, as you've already done), but if they fail, you're eventually stuck with pulling the diff carrier.
IIRC, the Toyota diffs are made similar to the old 9" Ford. Can't you pull the axles, release the driveshaft, and remove the rear carrier? It's not that hard, and you don't have to mess with the diff settings, as they stay intact with the carrier assy. Or, is the Toy diff not like the 9"?
The clearances are too tight in there to leave it in. If you're lucky, it has stayed low and not got sucked up into the gears yet. You are tempting fate every time you drive it.
Is it a 100% assurance that destruction will happen? No.
Is it a big risk that serious damage could occur? Yes.
We genearlly have three groups of people here at BITOG; the pratical, the minimalist and the anal-retentive ...
I find it ironic that some BITOGers will run synthetics for 5k miles for "cheap insurance", but yet others would suggest leaving a foriegn object in the diff with a "wait and see" approach ... I'm not particularly picking on any one person; I just don't understand the mindset of BITOGers at times.
As much as it might seem expensive or a PITA to deal with now, it will seem horrid later on when you ask yourself why you didn't deal with it now. If you're not up to the task, then pay to have it done.