Have you ever done the right thing when leaving a position - given fair notice and stayed to finish your projects - only to get the "cold shoulder" and be treated unprofessionally?

If yes, please share your experience and opinions about why this happened.

I’m going through this now, but for a volunteer job. I spent 5–½ years donating $33K+ worth of professional services and bringing excellence to an organization. For various reasons, I recently decided that it’s time to move on. I gave one-month’s notice and promised to help with the transition. Now, the person in charge is refusing to communicate with or even acknowledge me. I’m upset and trying to sort-through everything.