Its a hidden file
see
How To Rebuild Icon Cache In Windows 7 To Repair Icons
However I've had a couple of machines where the Adobe icon vanished like this - I got the impression there was some kind of file corruption as they icon only came back after I'd removed and reinstalled the Adobe Reader
trying to point the shortcut at the correct icon didn't work - couldn't "pick up" the icon from any of the files in the Adobe folder - not even from the exe or dll files