Did the company issued the SCN to employee on email or by registered post to his available postal address?? if not then a leave of mere 25 days does not confirms absconding, there may be several incidental situations, where the person was unable to inform. or may have informed through anyone else but it did not reached the management,
It is the issue between management and employee, if management is satisfied by his replies and ask him to resume then it is absolutely not a break of service but LOP leave, i.e without payment, However the management or upper HR division must have obtained a written request with reasons of absence, with promise not to repeat it in future.
Declaring such case without issue of SCN, as absconding may drag the management to legal issues, as if the employee can produce valid and acceptable reason for absence, and management get rigid for absconding .......then management has to pay notice fees and compensation also. it would get subject to labor laws as termination of service without notice by employer.
If the services of the employee was not terminated & his name removed from the rolls of the company, there is no question of new id, continuing with old id is correct & proper. If absconding is mentioned as misconduct in the company policy then disciplinary proceeding can be initiated against him by issuing him show cause notice & so on.
The question of issuing new id arises only when the name of the employee is removed from the rolls of the company. Your thought process has to change.