Then what has happened today at exam centre?

This same happened with me also but my exam is on 2 Feb.

If you have lost your Aadhaar card, check the GATE exam guidelines for accepted alternatives. Generally, the ID mentioned during registration is required. However, you may contact the exam authorities to confirm if PAN card or another valid ID can be used as a replacement. Carry a digital copy if needed.

https://gate2025.iitr.ac.in/