Wow, Best Buy employees just cost you 150 bucks and there is nothing you will be able to do about it at the store, you will need to sue them locally which I seriously hope you do because they keep, not lieing cause that implies they ment to deceive, so... allowing untrained and unecucated employees pass themselves as "experts" costing consumers asinine amounts. But, whatever, some things will never change.
ANYWAYS, the reason they wont work is because the Q550LF or L uses DDR3L, or low voltage ram, 1.35V as opposed to the DDR3 1.5V that the Best Buy employees told you, like so many others, would work in that system.
http://www.crucial.com/usa/en/q550lf/CT4516103
Will work, try this
http://www.crucial.com/
Scroll down a little, they offer 2 ways to find compatible ram and they guarantee it if you order from them.
Just FYI I don't believe there is a Q550L. There are 2 different Q550LF, the Q550LF-BB17T07 and the Q550LF-BS17T21.
Oh ok I see, I just flipped mine to check the sticker, you are looking at the black sticker, look to the side of the black sticker,. the one with the bar code, directly under the bar code will be the full model number.