Aparently the employee has sent resignation with immediate effect/without notice/without full noticeperiod asper appointment letter...................
If the has resigned then he/she has ended the employer-employee relationship and has not ABSCONDED AT ALL.
Absconder is a derogatory word and you/employer should avoid to apply it.
As per previous posts you should have checked the applicablity of notice period in this case as per enactments applicable to establishment/employer and If you have checked and are convinced that notice period in this case is NIL.........................then the T&C inserted related to notice epriod are VOID.
Aparently there is nothing in the matter and it may rather boomrang if you falsify the record.
There does not seem to be any breach by employee.
The employee might also have consulted and be properly informed and supported,by now, bu unions/counsel/lawyer.
However you must show all documents to an able Labor Law Consultant/Service Matters lawyer/Law firm and proceed further after understanding the merits.