Yikes, that's creepy. Same thing happened to me once, I swore I heard my mom. I just went and checked every single room, even closets. Turned out a window in the den was open a crack and it was just the neighbor's TV.
The part about checking every room is classic. Our brains are desperate to make sense of things when we're alone. I swear half the weird stuff I hear is just the house settling or a fan motor changing speed, but for a second my mind makes it a voice. It's like a weird glitch in how we listen for danger.