Hi! I had never heard of Louie Mamengo before and had fun searching for information about the beginning of his career and his famous designs. Did you know his parents wanted him to become a doctor?? I found more details about the beginning of his career in this article titled, "Designer Spotlight: Louie Mamengo" from the Phillippine Online Chronicles: http://tinyurl.com/atjfqbd.
I also found an article describing the fashion piece he was known for; "a figure flattering black gown". The article is very interesting and includes information about the people who wore his designs. The article is titled, "Fashion Week unveils Louie Mamengo’s last collection" and was found through the Lifestyle Inquirer.net. You can read more here: http://tinyurl.com/bgvdcog. ***I used tinyurl to make the links shorter for you. To locate both articles, I Googled: louie mamengo designs.
I hope this information answers your question. I am a library student and a volunteer at http://www.ipl.org. We love to answer questions like yours!