I'm not sure what kind of packaging that card came with, but virtually every graphics card I've ever bought that has an additional power connector on it has come with a big sticker on it saying something to the effect of "Do not under any circumstances use this card without the additional power connector attached and powered by an adequately rated power supply".
Those connections are NOT meant to be optional.
Plus the
adapters to connect them are super cheap if one wasn't included. Wouldn't you rather spend $5, instead of $500 replacing a graphics card?