From what I understand, to verify your employment they do a web search on the company to confirm its existence, check it's website, and sometimes contact the references you provide in your letters (supervisor/manager/HR). Though in my case none of my co-workers got any calls or emails, at least that's what they claim. In notes they did mention the other checks they did though. Ideally, you'd want some kind of reference other than yourself, so I don't know what they'd do in that situation. Have you ordered any GCMS notes before?