The ADA covers qualified workers with a major physical or mental impairment function that is long term, not short term. Christine is right about "reasonable accommodations," as long as it does not cause undue hardship to the employer, other employee's, finances, business continuity, etc. There are other factors involved, like the policy of your employer, past practice, and treatment of other employee's in similar situations. Some have no back to work programs, some do, and if you can't perform the essential job duties you cant work, being doing so would cause undue hardship. Even if re-assignment is in practice, you need to be qualified for that job.

I wonder how long your employer has accepted your disability, let you work, and accommodated you, and what hardship do they say now is the reason for discontinuance? I guess the doctors note put your employer "on notice" so they are doing the same with their intentions.

Everyone made good suggestions to follow-up. Another are disability advocacy groups that offers free help in your area, even lawyers. Good luck.