Getting a private message without signing in ?

[pallophotophone]

Hello,

A couple of days ago I received a private message notification via Email from a known member of this forum. I was able to open and read it without signing in.
Unfortunately I spent close to an hour and a half composing a reply. I was able to theoretically send it, according to the site. Unfortunately after I checked the sent emails, because I had a feeling that my message just went into a black hole and was not actually sent.

How was I able to access the members private email message to me without signing in and how was I theoretically able to send a reply to him-again without signing in ? ? And have it lost after spending so much time carefully crafting a considerate reply ?

Thank You,

Bob Hodge