Well, they aren't very professional if they abandon a patient in crisis - the time when their professional services are most in need, their skills are most attuned to problem solving, and their attention should be focused on doing what they are trained - and paid - to do.

If you think this is something they might do, whether it's just an unfounded fear of yours, or based on something you have heard or seen out of them, I would just bluntly ask them - you have a right to know who is treating you and what your treatment plan will be, and that includes continuity of care in the event that a provider is no longer able to serve you.