I don't know why the adoption group wouldn't want to work with you as long as you were up front with them about why you had to back out. I had to do the same thing, for similar reasons (sick cat), and when I was ready, I just let them know that things had settled down and I was ready. Of course, the dog they had initially suggested for me had been adopted by someone else, but as it happened, another dog that I had fallen for before I was ready to adopt in the beginning (If that makes sense?) had been bounced and was available. So, it all worked out and I got my heart dog
If for some reason the original group won't work with you, there should be others around (don't know where you live)?