I've never heard of a properly applied bandage deforming a hoof, much less to the extent that a crack is caused. However, an abscess that comes out through the coronary band can certainly cause a horizontal crack. Perhaps your vet didn't get it all or there was more than one pocket of infection.
If the crack is spreading or deepening, I would definitely get your farrier to take a look at it. It's hard to say what the best course of action would be without seeing it, but a hoof supplement might help it grow out faster. If the crack is from last June, it ought to be pretty close to the bottom of the hoof by now. I think 8 months is about the amount of time it takes to grow all new hoof wall if I'm remembering correctly. In the meantime, your farrier might have some suggestions to stabilize it and keep it from spreading.