Dear Aunt Bozette,
We are glad you got your invitation to the wedding. We are glad you think it is pretty, because we spent a lot of time and money on getting it printed-- which was precisely one of the reasons we decided not to deal with any extraneous printing stuff. Not only is the postal service inefficient and inconvenient; in an age of electronic options, it's become largely unnecessary. To this end, we started a wedding blog to keep people informed and to give them an electronic way to RSVP and let us know if they were coming. Since we don't expect people to be mind-readers, we opted to put the URL directly on the printed invitations, along with the (we thought) very direct phrase, "To RSVP, please visit X"
We were worried some of the seniors wouldn't get it, but surprisingly, almost everyone has managed to do this. Even 88-year old Bubbe Yid managed to pull it off (if only to email me that she couldn't come). You are the only person who got the invitation, assumed it was incomplete, and wrote me to say "My invitation is missing the RSVP card."
Might I suggest re-reading your card? Failing that, you can just skip the whole invitation entirely and email me to let me know if you're coming. You know, like you just did to complain about a nonexistent RSVP card.
Looking back on it, I can't imagine why we thought it wouldn't be a good idea to include extra pieces of expensive printed material that we would need to pay more to mail to you so you could mail them back to me so I could wait several days for them to come and learn about your ongoing struggles with literacy. Still, I suppose it's too late for that now. We'll all just have to suffer on, thinking about what might have been.
I hope this helps. I look forward to hearing from you.
Your ever-patient nephew,