I was hoping that if you haven't gotten an answer back from them, maybe you should try calling the service Dept. at 845-306-1000 and inquiring as to whether or not you will receive a response to the card. If many of you would make such a call, then maybe you might actually get some kind of response even if it is not a Thank you for donating blood on behalf of JWs. Otherwise I think they will just ignore the "You're Welcome card.
see. ajwrb.org, download the brochure to see what I am talking about if you don't know. This could be added to ACTION NUMBER 1, which is to donate blood and send in the You're Welcome card. If you can't donate your blood for some reason, try and get someone else to donate on your behalf and then send the card in.
I really hope they reply to someone's card.