Answer from Margaret, PHR, SHRM-CP:
In the event you’re made aware that an employee needs medical leave, but the employee is not available for direct contact due to inpatient care in a facility or incapacitation, send the applicable leave paperwork to the employee’s address on file. The employee may have someone who can get the paperwork from their home address to them or their health care provider—this is one of the most reliable methods of delivery to prove that you’ve met your compliance obligations.
It’s possible you’ll hear from a case manager, family member, or emergency contact who reaches out to you on the employee’s behalf. In such a situation, you could also send the paperwork to the employee at the facility they’re in.
Whatever the case, address the paperwork and any other correspondence to the employee directly, and don’t release the employee’s confidential information unless you have direct authorization from them.