how to sync iphone sysdiagnose to MAC osx

I have been asked to help shoot a possible bug in the iPhone/Bluetooth interface between my Lexus and my iPhone 6s.

The process should copy the file from the iPhone to the MAC using iTunes and its sync function.

It should copy a file called:

~/Library/Logs/CrashReporter/MobileDevice/[my device name]/DiagnosticLogs/sysdiagnose

Alas, such a file never gets copied.

The sysdiagnose is created by installing the appropriate profile in the iPhone, running a test then pressing the volume up, down and power buttons at the same time. When I do this there is a short vibration indicating something has happened, but that's it.

The sync says it's copying diagnostic files to the MAC but I cannot find them.

Can someone suggest what I might be missing please?

Thanks

Barry