Your screenshot does not show enough information to be sure because: the net names of the pads are not visible; the copper areas are not visible. I will therefore assume that you are just doing a 2 layer board and that the ground plane that you refer to is created by a Copper Area assigned to GND on the top and/or the bottom layer. I would guess that you have both pads 1 and 2 net named as GND and so when you did the copper fill an area of copper appeared around each pad which would also be assigned to GND. If however you did not check the PCB Design Manager and track down every last **Incomplete Net** warning before submitting the board for manufacture then you would miss that it is quite possible for those two little copper areas to be connected to GND through each pad assigned to the GND net but for them to not be physically connected to each other or to any other copper assigned to the GND net.