I put in a post concerning this and then got it dropped somehow. But anyhow, OP, do not worry about the fact that they may have told EDD something completely different than what actually happened. The department will work it all out, and will do so with the statements from both parties. They are not more believable just because they are the employer, and the agency works at making decisions with the assumption that one or both parties may be lying.
It's not anything you could sue the employer for, but what they say is going to be weighed against what you say, and the decision will go to the one who is "most believable" in this situation.
It is NOT necessary that you bring up some discussions that you had in the past concerning whether you were thinking of leaving or staying with this employer. That is not relevant to what happened while you were out on leave. Don't you be the one to bring it up.
It is only necessary to explain what happened at the point that you, completely unexpectedly were confronted with the news that you had been replaced while you were on medical leave. As has been explored, they didn't have to give you FMLA, since the business was too small, but even so, you were replaced by them, you DID NOT quit the job. You state, very firmly and professionally that you did not quit the job, did not give them a verbal resignation, had no intentions of quitting the job, and were fully prepared to return to the job when you were told by your employer that you had been replaced and that you no longer had a job to return to.
You will be asked to produce medical statements which will show you are fully released to return to full time work while filing a claim. These will, of course, verify that you left on xxx date due to medical reasons. Then you tell how on xxx date, you again returned to the work site and talked with supervisor John Doe, who told you that.... Just as it happened. Let them say anything they want, you just tell exactly what did happen.
If you are approved, be prepared for them to appeal the approval, which they have a right to do. If you are denied, you will be appealing the decision immediately. You don't need to produce an argument in the appeal, just say "I wish to appeal this decision." A hearing will be scheduled, at which both parties are invited to attend either in person or by conference call.
Even if you have won the initial appeal, you will, of course, want to participate in the appeals hearing if one is scheduled, to make sure your side of the story is told. Once again, you describe the situation as it has actually happened, let them say anything they wish to say about the reason you left.
There's no need for you to jump up and accuse them, question them or call them liars. Don't even be surprised, I once saw it happen, if the employer produced a trumped up letter of resignation that the employee had supposedly given them. All you need to do in this circumstance is state, at the appropriate interval, "This is not my signature, I did not write this letter, I never saw it before today!"
You keep it quiet, factual and brief. And you try very hard to be the more believable party, which when the truth is on your side, should become obvious to the adjudicator who is making the decisions.