It's a refinement of a very old scam. The more primitive form involves the scammer getting a name and phone number, calling, saying, "[name], it's me! Help!" and letting the mark fill in personal details on who they think the caller is.

The scam was easy for you to spot because, I imagine, you mainly correspond with people who write e-mail in complete sentences. A lot of people, like the victims on Facebook where this scam is making news right now, would find it perfectly normal to get grammatically e-mail (or internal Facebook messages) from their friends. They would also find it natural that the person used that platform rather than picking up the phone for an urgent message.

So basically, it didn't work on you because you weren't in the target demographic.