It the washer and dryer in your basement are operational, then there is a link to the outside. The dryer will have a vent to take warm air outside. If you're lucky, this vent is well sealed against the wall or ceiling through which it passes and the hose is tight on the duct connection. Otherwise, you need to check this area immediately and find a way to seal any small holes. Obviously, if you need to move the dryer to check the vent, you'll want to check very carefully around the bottom of the dryer to be certain that you don't pull the dryer over the top of your snake.
You'll also need to take the cover off the back of both the washer and dryer. These appliances could provide a dark, sometimes warm place for a snake to hide. I won't be at all surprised if she's there. These areas also have some moving parts, so you'll want to make this check before you use either appliance. While you're at it, please check the drain line where water leaves the washing machine and possibly the incoming pipes to be sure that there isn't a gap between the pipes and the wall or ceiling.
I sympathize with your feelings right now. I've only owned snakes for a couple of weeks and am just learning the ropes. My ball python is only 14 inches long. Her aquarium is 16 inches tall. Doing the math, I can't see any way that she could reach the top of the aquarium. I have a little climbing tree for her, but getting to the top would still be a reach. Somehow, she's making that reach. I've come home twice this week to find her clinging to the support bar in the middle of the top of her aquarium. Needless to say, I'm thankful that I went entirely to clips.
I wish you luck finding your little friend. She shouldn't have gone too far. With any luck, she'll turn up somewhere obvious in a day or so.