Because of the protocol implementation on Philips Hue bulbs, it is not possible to remotely factory reset the bulb. Instead a separate Philips Dimmer Switch is required to proceed. 

With the Philips Dimmer Switch in hand, bring it within 10 centimeters of the bulb or lamp you wish to factory reset, then press and hold the I and 0 buttons simultaneously.

Continue holding for 10 seconds until light starts flashing a few times. The bulb is not reset and can be reincluded.