Droid is one of the three skins released as part of the Ghost in the Machine offer. It could be purchased as part of an coin deal from late March to early April 2017.
Droid could be purchased for $9.99 in a limited time deal that included 16000 coins. It was not available for individual purchase and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.
Note: The Ghost in the Machine offer with the Droid skin was released again for a limited time in mid January 2019. The time the price was lowered to $4.99. It still included a package of 16000 coins.