If you are a foreign national on a trip to India on a visa and you lose your passport, you can apply for an Emergency Certificate and return to the city of your origin citing the reasons to do so. Further, such certificate is only granted when the concerned authority is satisfied that the case is not bogus or false and there is no hidden motive behind such claim of a lost passport.
If you are an Indian citizen who has lost his passport, you need to apply for re-issue of passport. Following documents must be submitted along with the application:
Proof of Present Address
Proof of Date of Birth
Affidavit stating how and where the passport got lost/damaged (Annexure 'F')
Police report in original
Self-attested photocopy of first two and last two pages, including ECR/Non-ECR page of old passport, if available.