Hr Is Saying My "resignation" Was Voluntary Even Though I Never Resigned. What Are My Options?

Location: California. About three weeks ago I was put on medical leave from my office job after a minor surgery, all paperwork went through our short term disability provider and I was told by my manager and HR that my job was safe as long as my doctor notes were current. I was approved for four weeks off. Last Friday I logged into our payroll portal to check my upcoming deposit and got a message that my account was inactive. I tried my work email and it bounced. I texted my manager and she sent back a screenshot from HR that said I had "voluntarily resigned effective Monday" and that my position had been posted. I never submitted anything. No email, no phone call, no form. The only thing I did was fill out the leave of absence paperwork they sent me. When I called HR the rep told me that because my original note said "may be cleared to return in 2 to 4 weeks" and I had not yet provided an updated note, they "interpreted that as you choosing not to return" and processed it as a resignation so they wouldnt owe unemployment. She literally said that on the phone. I now have no health insurance while I am still recovering and no access to the HR portal to download my leave documents. I saved the call on speaker with my partner in the room and wrote down exact times and dates. Is this actually legal in California or does this count as a wrongful termination situation. Should I be talking to an employment attorny or the labor board first. Is there anything I should or should not say to HR if they call me back.