Thanks to Hassath's urging, I gathered up the courage to visit the RPO
once more, to apply for ECNR
status ("emigration check not required").
The information counter gave me a copy of
form #2 for INR5.
I filled it in, attached a photograph and a self-attested photocopy of
my matriculation certificate, waited in another short queue at counter
#12, submitted the application along with my passport and INR300. I was
told that my passport would be returned by 1300, and that I should wait
in another queue to collect it. But I got my passport back a whole
ten minutes before 1300, and the ECR stamp had been deleted; the
next free page had an ECNR stamp, and all was exactly as it was supposed
to have been in the first place.
It's good to know that I won't have to go back to the RPO anytime soon.