I use many hotels not as a company employee but as supplier to them. It is common to actually be asked to use their corporate reference when they know I will be staying in their nearby hotel so they can increase their volume of business (which is tracked by the hotel and reported periodically to the company) as it helps them reduce their room rates in negotiations.
And if any hotel asks to see any correspondence between myself and my client as some sort of "verification" I would tell them where to go. But it's never happened.