It's not dead, it's just resting!

How tall is the plant? Did you repot it when you got it? A small michelia doesn't have a lot of roots, and the change in environment and/or repotting means it needs some time before it starts new growth, pinching it back just set it back a bit more.

Also, magnolias don't usually branch quickly when young, so you're better off waiting until it's talling to cut it back for more bushy growth.

As long as the plant's healthy, it sounds like it's got good conditions and it will eventually produce new growth, just hang in there!

Jim