My therapist has no cancellation policy. If it's possible to reschedule on a same day then that's what we do, another option is to have a phone session at the same time or a very early morning skype session.

Anything else is me missing my session. I haven't had a need to miss a session for a long time, especially after my T discovered that it's possible to have sessions over skype. For instance, I'm travelling most of the next week. This means that I can go in person to my Mon and Tue morning sessions, the Wed morning session is replaced by skype session and Thursday morning session is anyway skype session.