Yes the Transistor looks similar to the Temperature Sensor. They have the same black body with 3 legs
though the Transistor outer legs are bent whereas the Temp Sensor I have the legs are all straight.
Anyway I tried a transistor in the circuit and got varying negative readings like those in this thread.
So ensure it's really the Temperature Sensor and not one of the Transistors.
In my official kit I got 1X Temp Sensor and 5X Transistors which were taped to a card.