Your employer has the burden of proving you quit.
Your employer has a duty to accommodate your disability, if possible, but this inquiry is fact-specific. A great free resource is the Job Accommodation Network. http://askjan.org/ Given your situation, it would be well worth your time to call that agency.
Also try contacting a local lawyer in your state.
David A. Mallen offers answers on Avvo for general information only. This offer of free, general answers is not intended to create an attorney-client relationship. If you need specific advice regarding your legal question, you should consult an attorney confidentially. Many experienced California labor and employment attorneys, including David A. Mallen offer no-risk legal consultations to employers and employees at no charge. David A. Mallen is licensed to practice law before all state and federal courts in California, as well as the California Labor Commissioner and the California Unemployment Insurance Appeals Board. Failure to take legal action within the time periods prescribed by law could result in the loss of important legal rights and remedies.