I'm building a APRS tracker for a high altitude balloon and am tracing the voltage as it's not powering up. I'm confused why it seems that this capacitor's ground appears to not be connected to anything. topside of board
Actually, your picture clearly shows the pad to be connected to the top plane. Most likely that's ground. With the top plane being ground, how else would you expect pads to be connected to ground?
You can clearly see the connections between the pad and the plane at the 12, 3, 6, and 9 hour clock positions. The reason the pad isn't connected to the plane all around is because that would make hand-soldering difficult. With copper connected everywhere, the plane would act like a large heat sink, preventing the pad from getting hot enough for solder to flow properly. These arrangements of isolated connections and gaps are often referred to as thermals in PC board lingo.
You can see such thermals on the pad immediately right of the one you marked, on the right-most oval pad at lower right, and on the right pad in the row of 7 at bottom. All these pads are electrically connected to the top layer, which is largely a plane, most likely ground.