Your bud have blasted likely due to a change in location (when you brought it home), and the repot. It happens, it's sad but it happens. Please remember that sphag takes a while to dry out, so don't overwater. Also make sure the sphag is not packed super tight around the roots. I use sphag on some of my Phals, and they love it. Other members here however hate it, because it can stay too moist, causing the roots to rot.
Here are a couple of links for you in case you have not seen them. I use the skewer method for sphag and it works well for me.
Skewer use for watering of orchids AOS | Phalaenopsis