I've heard of this four or five times over the years that I've been with AdWords - especially during those years when I was on the phone. Although I have no details at all about about your business or its staffing, I will say in the past the cause for such oddities has turned out to be along these lines:
* a helpful family member who started an AdWords account to drive traffic to a home business, but without mentioning it to anyone
* a ambitious person within the company (usually in marketing) who started an AdWords account to jump start traffic to the site, but without checking in with 'the boss' about it first
* an account set up by someone within the business as a experiment or test "that was never meant to run", then forgotten.
If there are others in your business, you may want to send out an email to everyone asking if any of the above may have occurred. Also, don't forget to check your credit card(s) to see if there are any charges from AdWords.
I hope you get to the bottom of it - and maybe tell us what you find.