never thought; didn't think

I did n't think you were going to ask for cigarettes.
I never thought you were going to teach us about reducing plant stress here this morning.

Both the above sentences comes from the Corpus of AE. I'd like to know whether 'I did n't think' and 'I never thought' are interchangeable in such sentences.

And how about 'I hadn't thought'?

Could I ask native English speakers to help me please? Thank you very much.

I'd say that 'never thought' shows more surprise, shock, etc.