You can firstly check for the softcopy of your Hall ticket if available in your device. If not, then you can check your result, if you remember your roll number. Still if you don't remember, then you can obviously check your result based on the Registration Number.

Most probably you haven't lost your admit but after the examination of the NTPC or SSC the admits are taken by the exam center at the end of the examination.

To know more about RRB NTPC, visit the link below:

https://competition.careers360.com/exams/rrb-ntpc

I hope this answer helps. All the very best for your future endeavors!