I don't see anything in there that says keeping a list so you can reach your buyers is sufficient. It's all about the buyers being able to reach *you.* That is the point of the label. And if you rely on your information, what do you do if your buyers move, or get new e-mail addresses? How will you contact them then?
Nothing says it is ok not to mark if people can find that information on a website, either. The law details what is to be included on the mark:
"These markings are to enable the manufacturer, retailers and
the ultimate consumer to ascertain the manufacturer or private labeler, location and date
of production of the product, and cohort information (batch, run number, or other
identifying characteristic)"
http://www.cpsc.gov/about/cpsia/sect103policy.pdf