Sending random invoices to companies hoping they'll just pay without thinking about it is a pretty common scam actually. Here in Germany for instance you start getting dozens of fake invoices via ordinary mail the exact second you register a new company, and I guess it's not very different in other countries.
They're scam is that when they invoice - they hope that the company is big enough to the point where A/P just pays it when they say "Yeah so-and-so in IT confirmed this order" -- they are hoping that the initial contact and the AP departments dont talk.
