Sorry to hear of your friends loss and if I hear anythhing I'll let you know (not that anyone ever tells me anything)!
Security is a concern for most yards / marinas / dry stacks / etc. and I believe that most do take it seriously. However, you can't account for everything unless you want to take away the "user friendliness" aspect of your business. Afetr all, if you have 100+ customers and their friends and families wanting to access your facilities on a regular basis it is easy to take your eye off the ball.
Obviously, I don't know the exact circumstances off your friends loss or the security at the location involved, but I do know of businesses that claim to offer regular foot patrols / CCTV / Access controlled gates / etc. and the still have things nicked!
Hope your friend gets a good outcome in the end. I'm just off to check my insurance!!!!