Well, then you definitely have bigger problems. Since differential work is fairly specialized, and requires special tooling, I recommend you pull the differential from the axle and take it or send it to a good differential specialist. The work will be expensive. It sounds like your bolts were not assembled with locktite and worked loose over time. It is highly likely your gearset is damaged and your ARB locker may be as well.
I can personally recommend Ken
@gearinstalls.com . He is the master of Toyota differentials. Go to his site and see what is involved in setting up a differential, and you'll see why I STRONGLY recommend you not tackle this yourself.
The stock Toyota bolts do not have hardness markings, so it's likely your existing ones were the proper ones, either not torqued properly, or no locktite was used.
Good luck, post back what you end up doing.