Even though there might be other possibilities, checking the roots is a good move. If the roots are okay, that’s great news and you’re on the safe side. If you discover rot, you can just cut off the bad parts and the repot the plant. That causes severe stress, so it might take a while to recover, but it’s the only way to help with root rot, as otherwise it will only spread, killing the plant in the long term.

I have three spider plants that used to take turns spending a month in the windowless bathroom. They’re all fine. There was at least some sunlight coming in from the surrounding rooms though.