A code P0135 means the sensor heater circuit is open or shorted to ground. This would be because the wires were cut, the O2 sensor was badly damaged, the connector came loose, or the grounding of the sensor heater circuit got messed up. It does not indicate silicone poisoning.

The heater is just a chunk of wire that gets hot when current passes through it. It is intended to heat up the actual oxygen sensor so it will give accurate results as soon as possible. The heater turns on with the ignition. The element should be 2 to 5 ohms. You should find 12 volts present in the harness coming to the sensor.