The guard had noticed the back doors of a lorry were open at 4.50am on Tuesday and on closer inspection saw a man jump out and run towards a white van.
While attempting to take a photo he was struck from behind with a metal object and hit on the ribs and head before losing conciousness.
Police and paramedics arrived at Watling Street, Four Crosses, shortly after and the security guard was taken to hospital.
Staffordshire Police is now appealing for information concerning the theft and revealed that boxes of shoes and slimming shakes were stolen during the raid.
A spokesman for the force said: "The guard witnessed a male, described as Asian, and seen wearing a dark-coloured turban, a black jumper and navy blue jeans, jump out of the lorry and run towards the driver's side of a white van.
"As the guard attempted to take a photo of the van, he was struck from behind with a metal object by another offender. The victim was struck in the ribs and fell to the floor losing consciousness.
"Shortly after, the victim was treated at the scene by paramedics and taken to hospital for treatment. It is believed boxes on this lorry were damaged and boxes containing shoes were stolen."
The spokesman added: "Another white lorry was reportedly broken into where slimming shakes were stolen. Police are currently investigating and are keen to speak to anyone who may have witnessed the incidents.
"Officers would also encourage anyone who may have dashcam footage of the areas at the time of the reported thefts and criminal damage instances to get in touch."
Contact Staffordshire Police on Facebook, Twitter, or call 101, quoting incident number 063 of April 12.