If the employer didn't see the original visa prior to employing this person they should have used the Employer Checking Service (
http://www.ukba.homeoffice.gov.uk/sitec ... equestform) to get confirmation of right to work.
Failing to do so may be seen as an indication that the company lacks sufficient systems to prevent illegal working, which could have a negative impact on the licence.
Could be worse if the person applied for ILR after their visa expired - as then he'd be working illegally.