How do your friends know that the security tape wasn't reviewed? But, bottom line is "squeaky wheels". Why don't they ask hotel security to do so and report any suspicious findings to the police. If they don't get a positive response, elevate the request to hotel management.

This is a public forum. Other people look. The bottom line is that if you are parked in a public lot, don't leave valuables in the car. The fact that someone else didn't have their iMac stolen doesn't make it any smarter for the next person to leave one.