I hope it never happens to you, but if your passport gets lost or stolen while you are in India, there are a few things you must do immediately:
1) Call your embassy or consulate. Keep the number programmed into your phone. Even at night, there should be a duty officer on call for emergencies.
2) Go in person to the local police station and file an FIR (First Information Report). This has to be filed where it happened, not in another district. You will get a signed and sealed copy of the FIR, which you must keep safe. This is usually a one or two page document with details of the loss or theft. Don’t part with it, as you will need it not only to get a new passport, and also to get en Exit Permit. Incidentally, you should take someone with you to the station, especially if you are a girl. An older, respectable Indian who can help translate would be ideal.
3) You will need to go to your embassy or consulate to get a new passport. Generally you have to go in person, but there may be exceptions. I’m not sure about that. You need to bring a passport size photo or two according to their requirements (check the exact specifications) and your FIR. You will be issued an emergency passport to allow you to leave the country. For Americans, the document is 12 pages long all together and no pages can be added. There isn’t room for more than one or two visas at the most, so it’s not good for extended travel. US citizens can also apply for a full passport at the same time and there is no extra charge if you get it within a year (highly recommended even if you have no further travel plans). That one has to be sent from the US, so it takes a couple of weeks, depending on where you choose to receive it. Incidentally, for US Consulates (and probably many others), what you can bring inside is restricted and not all have a place you can check your bags, laptops, phones, etc., so call ahead to ask. The embassy in Delhi does have a kiosk where you can check your items, but some others don’t.
When you passport has been lost or stolen, you can’t transfer your previous visa to it, no matter how many years are left. This is because the visa has the old passport number on it, so a transfer is only possible if you still have that passport. Unfortunately, many visas are only available from your home country, and this is getting tighter and tighter.
4) Next you have to go to the FRRO or FRO (Foreigners’ Registration Office) to get an Exit Permit. This theoretically takes about five days to process, but be sure to check with them before you book your flight to make sure you allow enough time. I’d recommend allowing a few extra days in case of bureaucratic snafus. Most likely, they will want you to leave within two or three weeks, but you should ask to be sure. If you already have a ticket and it’s a few months off, they will probably want you to leave sooner.
To get the Exit Permit, you have to bring proof of a confirmed flight out of the country, the original FIR, a passport size photo, and address proof (where you are currently staying, not your home address), registration papers if you are registered, and maybe some other documents. Hopefully, you have copies of your old passport and visa and entry stamp (you should always copy these items and store them on the cloud or email copies to yourself.) Count on at least two or three trips to the office. Go early and bring something to do while you wait.
The address proof is tricky if you are staying in a private home or anywhere that no C-Form has been filed for you. All hosts are supposed to do the C-Forms for foreign guests, but the reality is that many people still don’t know, and some of the states don’t have their system together. The problem is that if there’s no C-Form, your host has to go to court with his identity proof, utilities bill, etc. and get an affidavit. This is not a fast procedure and it’s not likely to happen within a day or two. If you are already staying in a hotel and they’ve done the C-Form, the only thing they have to do is provide a signed and sealed letter on official hotel stationery. You can’t shift to a hotel to get it, though, because they can’t file a C-Form without a visa. It’s a classic bureaucratic catch 22. It’s a huge waste of time and a big headache, usually involving multiple visits to the FRRO and court.
Be sure to keep original receipts, letter(s) of notification from the embassy, and any other paperwork from the embassy or FRRO, etc.—in other words, keep every piece of paper that could possibly be related to the case. Keep all your documentation even once you are safely out of the country. If you apply for a new visa to India at some time, you may need it. Seriously. Even if it’s five years from now, you might actually be expected to come up with the original FIR. You just never know.