Update:

I flew yesterday. The check in guy in Phnom Penh made only a cursory glance at my ETA paperwork and didn't notice that passport number was wrong.

Transiting Kuala Lumpur, no one asked to see it again.

Landed at Chennai Airport at 11 p.m. Went to the e-tourist visa booth. Immigration officer took my paper and typed in the visa number and swiped my passport and then did that again, and it was clear something was "off."

I explained that one of the digits on the ETA passport number differed from the actual passport I had uploaded. He conferred with colleagues and said he would have to discuss with the supervisor.

I was led away from the booth and told to sit outside the principal's office. OK, outside the immigration airport boss' office.

Various officers came by and looked at my documents and commented on the situation and some said it was a problem and I should reapply. I wasn't sure if they meant "you should have reapplied ten days ago when you noticed the error" or "you should reapply now"

Met with the immigration boss, explained the error, showed him the follow up email when I contacted the evisa people by email about the error and they responded "you can travel to India." That document actually seemed to satisfy him, though I also sucked up by saying I realized he was the boss and it was ultimately his decision.

I was asked to have a seat again while he made a call about it, received a call back, and then spent a long time typing up paperwork about the incident. One document was titled "memorandum" and described what happened and was cc'd on several people. More immigration guys came in and asked what flights I was on, asked to see/photograph my boarding pass, asked if I had told Air Asia check in staff about the error (of course not).

They asked if I had a checked bag and photographed the bag tag.

Their questions about Air Asia led me to believe they might try to punish Air Asia for this, and then I saw that one of the documents they were typing up saying something like "notice of carrier liability" and described Air Asia's involvement.

Shortly before midnight, everything was completed and I was led back to the e-tourist visa booth where the immigration officer stamped me in.

I then had to stand in a five minute line to go through the regular immigration booth line, even though I was already stamped in, because that's what they told me to do.

I got up to this second booth and showed the guy my new stamp and he asked if it was my second entry and I said no I had had just been stamped in for first time at the evisa booth. He said "just now?" I said yes.

He said "This date is wrong. It says 23rd, today is the 24th."

It was 12:04 a.m., you see.

He led me back to the e visa booth so he could question the officer who had stamped me in at 11:58 p.m. on the 23rd. He was satisfied with the guy's response and let me through.

When I got to bag claim, there was a young airport staff member standing next to my bag watching it like this was his only job for the night and he was quite happy to release it to me when I showed him the baggage tag.

Anyway, my advice to anyone else in this situation is just reapply. I'm a lawyer (they never did ask that), I like arguing about things, I've been to almost every country in the world, and I kind of wanted to see what would happen here if I showed up with an ETA on the wrong passport number.

My experience and gut feeling and research told me I could enter with the messed up documentation and wouldn't be deported/refused, and I was correct.

I was never really worried about being refused, but perhaps that's the arrogance of being a white male American passport holder who knows that generally I'm not going to be targeted for abuse by immigration officers. I wouldn't want to be an Indian lady trying to enter the USA with incorrect documentation. Nor would I want to be a black guy from Ghana trying to avail myself of India's e-visa with an ETA with the wrong passport number.

For most people, this situation of arriving on an incorrect ETA would be too stressful to make it worthwhile. I also hadn't considered that I would be inconveniencing a half dozen immigration officers due to my fat fingered error and maybe getting Air Asia fined and maybe getting a Cambodian check in guy in trouble for not noticing the discrepancy. All to save $75. Not worth it.