I have known, as acquaintances at monthly potluck get-togethers in our small mountain town, two gay men who have adopted two small children 4 years and 8 years of age.
This Xmas, they sent our 'E-Vites' to a chili party the day after Xmas. I accepted and then realized that we could not make it. I emailed on the 'response' f the E-Vite website and also emailed their personal email address to inform them. I then ran into them at the supermarket to say reiterate that we could not make it, we were sorry, yada, yada, yada, but that we had some presents for the children and would send them with mutual friends.
My friends delivered the presents to one of the parents and I have heard nothing since! No thank you via email, phone, snail mail, etc. I will most likely run into these 'obviously too busy to say Thank you' parents at this month's potluck and I don't know what to say IF I am thanked at this time. I am tempted to say (icily), "Oh, you DID get them?, I'm so glad..." But, my upbringing says otherwise.