Google definitely does not share their addurl info with Alexa. Alexa gets its URLs from usage of its toolbar and from web discovery (links found on other sites.) So, either your link was found on another site or an Alexa Toolbar user visited your site.
You will probably find that Alexa also crawls deeper and more frequently than Google.
Alexa often gets their information from DMOZ directory... are you there?
If you were to look up our site, it is listed on Alexa as Widgets - Nowhereville (city name) which is what the old listing in DMOZ says from when it was a local site (years ago).
Alexa uses that as their site title unfortunately. Oddly, nothing I do will get DMOZ to change it, while one of our competitors gets to falsly promote his site... no response to my complaints either, but that all is another issue...