I've been learning about this in my counselling training, in particular 'door knob confessions' which is when the client spills something as they are leaving that their t doesn't know and it can be quite an important revelation.

Some t's will mention it the next week, but other t's will not bring it up unless the client does throughout the rest of the therapy.

We learned that if a client mentions something, subconsciously they are 'ready' to speak about it.

Take care