Very gently pinch or squeeze the tube between your fingers, if the worm is still alive inside the tube you will feel it "jerk" inside reacting to you touching it. If all it did was loose the "feathers" it probably is still alive. Feather dusters often loose their head when something stressful has happened. I think A 10 degree drop would have been a very stressful situation to everything in that tank, just some deal with it better than others. If you have any fish, watch them closely, it is likely that a parasite out brake may happen too.
As per keeping the temperature stable, I have a few ideas. I don't know what lighting system you have (p.c.'s or M/H) but assuming that the aquarium isn't being over heated while the lights are on, I'd suggest that you adjust your heater to equal that of the warmest temperature your aquarium experiences. Even if it is a few degrees than you want it to be, It is far better that your temp going up and dowm. If the heater you have let your water drop to 70, ditch it and get a new one and don't go cheap. Cheap heater fail and one way or another wcan kill your tank (over heat - etc.) The Ebo - Jager is a great quality heater without brakig the bank to mention one. Also, the ambient temperatur of the room the aquarium is kept in must be fairly consistant. On that small of an aquarium, it is easily influenanced by room temperature.
Hope this helps,
Joel
