LinkedIn's Down

Hi. I would like to ask a general question perhaps related to Tomcat which I don't know too much about:

when the site came back up, I tried to log in with my usual email address and password, but received a message saying that there was "no record of my email address" &c.

I then proceeded to go through password reset which was successful. Generally, what could cause this to happen? Is there some type of delay or stale cache etc? DISCLAIMER: I realize this is really a question for LinkedIn, but wanted to ask of others if there were similar experiences. I am just now starting to understand what Tomcat does. Any info or thoughts appreciated. Regards.