Real Yahoo Mail Origin

I received a yahoo e-mail from a friend who lives in Bogota. I want to know where it was sent from so I go to the bottom right hand corner of the e-mail and click on Full Headers. That shows me a long list of info. One of the first headaings is X-Originating IP but I skip that because it's the address of yahoo and go down to Received. I copy that that IP to whois and that query results in LACNIC with an address in Potosi, Uruguay. I know my friend isn't writing from Uruguay but there don't appear to be any more IPs listed on that page so where do I go from there?