The transition from "short-term rehab" to hospice is not unusual. For reasons as varied as payment for a bed in a skilled nursing facility (SNF) to discomfort in giving bad news to families, it has become all too common for a patient to go to inpatient rehab to "get better" when the service most needed is hospice.
Rehab can still be done with a patient on (or starting) hospice. The expectation is simply different. The goal of rehab is comfort, such as reducing muscle constriction or added mobility, as opposed to recovery. This is an important distinction for your patient and for their family.
The Guide to Hospice and Palliative Care can assist you in speaking with families regarding the choice of hospice and what it means for them and the patient. The guides to advance directives and to rehabilitation can also be useful during these conversations. Having a clear picture of what it takes to do rehab and a thorough understanding of the patient's diagnoses and, most importantly, prognosis, can ease a family into their decisions.