Etiquette woes - I need help!

[RedRoseSAI]

Ladies (and gentlemen too, I suppose), I need your help. I'm finding myself in a sticky situation and I can't seem to find the solution in any Emily Post book!

Here's the situation: Mr RedRose and I were married about nine months ago. I dutifully sent out our thank-you cards recently afterwards. Just recently, though, I've found out that quite a few of the intended recipients never received their cards! I know of about six people so far, and from what I remember, they were all mailed on the same day. I feel horrible that they never received their cards, and I'm really not sure what to do about it. Do I re-write thank you cards to everyone I think was done in that batch? Do I re-do ALL of them, just in case? What do I say? Anything I can think of along the lines of "Just in case you didn't receive our first card, here is another one" seems so trite and lame. Still, these people need to be thanked!

Please help me, GCers - this is really bothering me!