It seems like an investigator could find out the insurance that was used by Dunham while in the hospital. Might not be easy but could be done.
from the link at NewsBusters:
“...Scott writes that Dunham, who wanted to be compensated for those costs as well as for her living expenses, “filed a separate claim under her employer’s disability insurance policy.” It was that claim, with the insurance company CIGNA, that was denied in August 1995 because, CIGNA investigators said, Dunham’s condition was known before she was covered by the policy.”