@Carol6290 While I'm sorry you had such a terrible medical event, no, you were not robbed. Guests are held to the cancellation policy in place for the listing.
You wrote: "I assumed we could get a refund because of the policy Airbnb has about unforseen extenuating circumstances beyond your control."
You should never assume anything. You have to actually read the policy. This is what the EC policy says:
What is not covered
Everything else. This Policy only allows for cancellations for the Events described above. Everything else is excluded. Examples of situations that this Policy does not allow cancellations for include: unexpected disease, illness, or injury;"
So as you can see, it specifically says that unexpected illness is NOT covered.
As you were already well aware that you have a pre-exusting medical condition, you should have purchased travel insurance, which would have covered you for this.
Airbnb hosts are not your travel insurers, who should lose out on their business income for whatever reason a guest feels they deserve a full refund. And I can assure that all guests think whatever reason they had to cancel, be it a major medical issue or that their friend can't make the trip with them, deserves a refund.