I'm having trouble getting to the gist of your issue.

*You injured yourself at work and filed the injury claim late.
*The doctor's office refused to provide documentation of the injury and the diagnosis.
*As of yet you have not filed a claim and don't know whether or not you have the right to.

I have some scattered thoughts.
1) Indeed, Workers Comp is completely a state-by-state adjudicated fund. If you need information on your state's law and the website is down, you'll have to find paper copy of the law. You work for a law office--I would guess this to be a great resource.

2) Usually you have to be off work due to the work injury for a certain period of time before you can file for Workers Comp. Some companies require you to use up all your sick leave and vacation days off before a claim can be filed. By the time you've used all those up, your foot may be healed.

3) These are dangerous waters. I would consider filing a Workers Comp claim to be a last ditch effort of desperation. Even though by law you cannot be fired for filing the claim itself, there is no guarantee that if you leave your job because of the injury the job will still be available when you're ready to return. They do not have to hold your job for you.

Any such claim will be reviewed by the state Workers Comp board/committee/whatever. They can either deny or grant the claim. If they deny you can file an appeal. You'll have to hire a lawyer for that. This process can literally take years. You'd need reams of documentation proving that you are no longer capapble of performing your job due to this work injury. You will have to prove without a doubt that this injury was not pre-existing nor incurred off the job.

And, perhaps you've never really noticed it before, but a lot of job applications have questions regarding previous Workers Comp claims made. If you check the "yes" box you'll need to fill out the next box with an explanation of the injury and the length of time you were off work due to the injury. Many companies will throw any application in the trash if the applicant has ever filed for a Workers Comp claim. And if you have suffered an injury they might not hire you due to the health insurance premiums/liability that they would be responsible for.

If I were you I would consider filing a claim only in the most extreme and debilitating case. Be careful.