My wife's 2005 Jeep Liberty does that from time to time, always has. Granted, it now has over 260,000 miles on the original engine but it does not burn one drop of oil and has never left her stranded. I went through the "why ?" phase with hers, could never find out why except for one time I didn't have the cap on the bottle fully tight.
There is no rhyme or reason why it drops, it can go 10 months or more at full, the one day it'll be half empty. She travels the same route to work every day, no heavy traffic as she leaves at 0-dark-30 each morning. No staining in our driveway, no coolant smell when you pop the hood, it's just GONE. I replaced the cap on the bottle with a new OEM, made no difference. It never overheats, gauge never gets above normal, the bottle is just low.
Since that is the only "issue" whatsoever with that vehicle, and I mean the ONLY ISSUE, I just keep tabs on it. More so now that I own a Renegade; I have to check my oil weekly due to the "David Copperfield Effect" of oil in these infamous engines, so I incorporated checking her coolant at the same time.
A little advice though. In your Renegade, DO NOT pour in regular off-the-shelf green antifreeze. It's not the same as what's in your cooling system. Sure, the bottle will say "compatible with all types of antifreeze", but DON'T. Mixing types of antifreeze can actually gel in your system, something you don't want. For a little top-off, use distilled water, never regular tap water. Bite the bullet and pay the insanely high price for a gallon jug of the right stuff from the dealer. It'll hurt your butt a tad for a bit, but it's cheaper than replacing the engine or cooling system because you wanted to save a couple bucks on a gallon of coolant.
Others may chime in saying "you don't have to use...", "you can use this instead" "don't pay dealer prices" "you're foolish to believe that 'special coolant' line", etc. or any of the numerous paranoid conspiracy theories people have about using factory/dealer parts, but I don't pay them any attention. I'm way too old to play the "they said use this, but I used that, and I saved XX dollars !! Neener-neener !" game. I use what the factory says thereby you can't go wrong. If something does happen, they have no argument. You used THEIR product, your purchase is in their computer. That alone is worth the couple extra bucks.