You're fixating on the number rather than the result the links bring you in traffic or some potential search value. Rather than spending time to know every link you should really be working to develop more relevant partnerships to get your site out there. Some times search engines will acknowledge a link, sometimes they'll give it weight and here's the real kicker: sometimes the link actually brings you relevant visitors its self!!!
p.s. if there's a particular site you feel you should have a link from then, as mike said, go visit it to look