I don't see anything wrong with asking- it's your home that someone changed things around in, asking why isn't nosy, IMO.
Something like "Hi XX, I'm struggling to figure out why all the appliances and electronics were unplugged and baby-proof covers found on all the outlets. I'm sure there must be some simple explanation, but I'm coming up empty- could you enlighten me?"
It is possible that she had a baby there, like at crawling stage, and was just really good about cleaning up all the evidence except for forgetting to remove the covers and plug things back in.
Now you've really got my curiosity up, too. Please come back here if she answers and let us know.
@Sosse1