GET request webhooks question

Hi, I have a question about GET requests using webhooks. I have my particle sending data to Thingspeak using a POST webhook, which works fine. But I would like to be able to get the most recent data entry from that channel on setup(). That way if my particle restarts or whatever it can get back in sync with the most recent data. So my question is how do I GET webhook data created using a POST request? Thanks