I'm creating opportunities automatically for our reps via custom function with email clickthru triggers. Is the Pipeline field not exposed via the API?

I don't seem to be able to set the "Pipeline" field via API.

- I've checked the API value and it is correct

- I've done a pull of a deal/opportunity record via getRecordById but the "Pipeline" value does not show.

Rep sends email to client with specific email subject. If recipient clicks link within the email we automatically create an opportunity for the rep and set a specific pipeline and stage value.

Any help appreciated