system
A chat on subreddit /r/pcmasterrace
human
That's a capacitor. It's used to filter out frequencies and the circuit can function after losing one.

The one you lost was between the first 3 pins, which are 12V power delivery pins, and the ground (shielding covering most of the board). It's meant to filter out spikes or instabilities from power delivered to the card from the motherboard through those pins.

There are multiple of such capacitors on the power delivery distribution on multiple positions. There is most likely a mirrored capacitor on the mobo between those 3 pins and the ground.

I wouldn't worry that much if my card wasn't clocked to the limits, my mood was a decent one, most of the power was provided directly from the PSU and not the mobo.

That being said I would try to solder it myself.
gpt
Wouldn't suggest soldering it back on to everyone unless you know what you're doing, holding a hot iron on there (especially if the capacitor sits across the ground plane of the pcb) could cause damage