I donate blood to Red Cross in California (most recently about a month ago) and have also never gotten a postcard, but they do have a pretty cool app now (calle

I donate blood to Red Cross in California (most recently about a month ago) and have also never gotten a postcard, but they do have a pretty cool app now (called "Blood Donor") which tracks your donated blood through the various stages of their system (processing->testing->storage->distribution). I'd assume any postcards sent out probably happen at the distribution stage, when the blood is shipped out to a hospital as that is a close enough approximation for the time when it will be used.