Despite a widespread and mistaken belief to the contrary, no law prohibits an employer from terminating an employee who is on short (or long) term disability. Collecting disabilty benefits does not convey any job protection on you. FMLA, which can and frequently does run concurrently with STD benefits, provides up to 12 weeks of job protection.
Assuming that FMLA applies, you cannot be terminated FOR REASONS CONNECTED TO YOUR ABSENCE for 12 weeks. At the end of 12 weeks, your employer has no further obligation to hold you job for you any longer, regardless of whether you are collecting disability benefits or not.
If FMLA does not apply, then your employer is not obligated to hold your job at all.
If the employer wishes to view this as a voluntary term, they may, and no law will prohibit them from calling it so or marking your file as such. However, their opinion as to the term being voluntary is not binding on the unemployment office. While you cannot collect UI if you are medically unable to work, when you are medically cleared to return to work I would expect you to be able to collect regardless of what your employer calls it.
Your termination will not affect your STD payment unless your policy is EXTREMELY unusual; in 26 years of admininstrating employer sponsored group benefits I have never seen and only once heard of a plan where benefits stopped with your employment. Assuming your employer has more than 20 employees you will be eligible to remain on the health insurance at your own expense (COBRA). They have up to 44 days to advise you of your right to COBRA (which will be retroactive to the date of cancellation); you will have 60 days to elect COBRA and 45 days from the day of your election to make your first payment. They MAY legally cancel your coverage until they receive your first check, but they MUST make reinstatement retroactive to the cancellation date.
