This is a complex situation and probably will require you speak to a workers' compensation attorney.
That being said, if an employee made false or incorrect statements about the manner in which he was harmed, where it happened or when then I know of no law that would limit the employer's ability to terminate for that offense.
This answer does not constitute legal advice and you should contact an attorney to confirm or research further any statements made in this answer. Any statements of fact or law I have made in this answer pertain solely to New York State and should not be relied upon in any way in any other jurisdiction. Additionally, we also encourage you to reach out to us via Twitter (https://twitter.com/#!/WhiteRoseMarks) or Facebook (http://www.facebook.com/WhiteRoseMarks) if you have follow up questions as we do not monitor questions after providing an initial answer.
There are so many details that aren't listed here. I agree that consulting a worker comp attorney is probably the best course.
Examples of such details include:
Was the employee treated by a doctor? What was the injury? Did the injury affect memory? Why can't the employee remember? Did the employee do something against company policy that caused the injury? Were there witnesses that the injury occurred, prior to the employee leaving Friday? I presume that the employee was off Monday and Tuesday except for being called in? and the absences were related to the injury?
The above is not intended to be legal advice, but may be used for general information. Please contact an attorney for specific help tailored to your needs. www.figgardenlaw.com