You often read/hear of people getting overcharged, but this time I got undercharged, and my conscience is bugging me.
Today I went to a restaurant that's locally owned, mom & pop kind of place (actually maybe just mom, no pop). I've been here twice before, the first time alone, 2nd time with 2 others, and this time with 6 others. The owner clearly recognized me. Our group got comped dessert on the house (sticky rice in coconut milk, yum!) which was a nice touch. I got the bill: $79.78. I collected $14 from each person since service was really nice (though sparse) and $13 each would have left a tip less than 15%. I added another $2 to make the bill an even $100.
When I got back to work I took out the bill so I could write down a list of what we ate & the prices (I took home the sheets our server used to write down our order, with prices added next to each dish).
Then I noticed there were no prices next to the softdrinks. And then I noticed there was no line for tax. Then I added up all the prices and it came to $90.65, not $79.78. Includng the softdrinks, and including tax it should've been ~$102. So we paid LESS than the total should've been before any tip.
I'm returning next week with a different group and I'm not sure what I should do. I can't inflate the tip next week since I can't expect that group to subsidize today's lunch! Do I slip a $20 to the owner discreetly? Will she be offended? Do I return to the restaurant on Monday, order a drink and pay $20 extra?
How do I know if she made a mistake (I was kind of rushing her to tally our bill), or if she wanted to partially comp us so that we'd return/spread the word etc? (She knew I'm returning next week since I made a reservation when I went up to ask for the bill)
Or do I just shrug it off, feel happy that someone was nice to us, and spread the karma some other way like dropping a $20 into the donation box next time I'm at my local State Park?
I guess I've never had this experience so I'm not sure what to do.