I walked out and / or 'quit' abruptly on several occasions in the course of my therapy (and with several different therapists). None of them contacted me, but waited for me to recontact them. Ethically that is what they are supposed to do.

With my long term T (8 years) I unexpectedly announced in one session that it would be my last, and I didn't go back. My t did eventually email me to see how I was doing... 3 years later! I guess she figured her ethical obligations had expired by then!