healing time for hairline fractures?

Can anyone tell me what kind of medical attention a hairline fracture requires?
I have an employee at work who claims he had a hairline fracture on his tibia (explaining why he missed work).
First he had “physical therapy,” which included TENS unit-type treatment (electro-therapy).
He returned to work about a week later, no cast, no limp, no evidence whatsoever of any kind of injury.

Have we been had? Or is it normal to recover so quickly from such an injury. (BTW, thi sperson is approximately 50 years old and has a variety of minor physical ailments).

Ask him for a doctors note along with number at which the good doc can be reached.