Greenwhite,
You may want to consider this.
I do 15-30 valet parking shops a month looking for cash integrity issues. I know of more than 100 shoppers who specialize in this work. I have mentored many of them. Most of them work for MSCs that do ONLY cash integrity shops and whose clients want a small cadre of specially trained shoppers to do ALL of their cash integrity shops. Unfortunately, the client in your case apparently was not working with a specialized MSC, since many that do parking valet shops are not routinely looking for integrity issues.
The reason that most of the large parking management companies, and hotels, pay for these shops (usually much more than you were paid) is that shoppers' reports (some including video) have shown that they lose thousands of dollars a month, per location, to organized "diversion" of cash by staff. These are not amateurs. Some methods are very sophisticated. In NYC police recently found a stash of over $40,000 in cash in the apartment of a valet parking supervisor. Many of the valet who worked with him were caught, on video, stealing.
That said, if the client in your case was smart, they would have followed up on your report and ordered a series of video shops so that they had irrefutable evidence to show to both the valet and, if necessary, the union steward. The unions do NOT want to waste money on arbitration hearings in defense of members who are on video stealing cash, so they usually advise the perp to quietly resign and depart.
Based in MD, near DC
Shopping from the Carolinas to New York
Have video cam; will travel
Poor customer service? Don't get mad; get video.