I can't imagine that you touching it caused it to burn up.
Usually caused by one of two things:
- Some of the three motor wires are touching metal to metal like bare bullet connectors are touching.
- Bad connection in one of three motor wires (bad bullet solder joint usually, but it can be a bad motor or bad ESC too) is like one wire is disconnected. This makes the motor just jitter and jump a little when you try to start it. It looks like it will run if you just give more throttle. You give more throttle and it burns out because of the missing connection (ESC tries really hard to make it start when it won't). If you ever see it jitter when you give a little throttle, do not give more throttle just to get it to start. If it doesn't start normally with just tiny amount of throttle, there is a problem to be found and fixed or you could burn a motor/ESC.