3 day rule is total crap by way of empirical testing. The very idea behind the 3day rule is insecurity... "She will think I am desperate". That's really paranoid. Chances are guys who think like that really are desperate in the first place. IMO the way to not seem desperate is to not be desperate in the first place.
The other aspect of it... "if she's not interested enough to remember me after 3days, why bother?". That's actually a better line of reasoning for Internet hypothesis, however, empirically it's total crap. Girl's who considered flaking but decided not to based on a goodnight phone call often end up LTRs.
Sinn has a guide to how he does phone game that you can find on mystery's forum, and Juggler has his phone ideas (probably in his ASF archeive). We need to update the bible in this respect.