How can you reverse engineer a websites paid traffic strategy?

I am trying to figure out where my competitor is getting his paid traffic from. I know for certain he is using paid traffic, I just can?t figure out where he gets it from.

I have used the usual tools for SEO (Market Samurai, Traffic Travis, Majestic SEO, ahref, SEO Power Suite etc) however they all return SEO results.
I have used SpyFu & KeywordSpy to see if that particular domain shoes any results for paid traffic. But both providers return no results.

I have also used moreofit.com…

How can you reverse engineer a websites paid traffic strategy?