Yeah, she never heard of it happening before...bullshit. It happens all the time. It's happened several times to me, and I don't even stay in hotels that often. One time people came in our room in the middle of the night, having just booked the room we were already in.
Maybe in your case they just hadn't made up the room yet. Usually, it's probably human error.
I suppose there was at least one advantage to the old days when there were physical keys.
Yeah luckily for us we didn't actually walk in on anybody, but didn't stick around just in case!
I'm sure it was just the case of beds not been made ect but at that time of the night we were exhausted and wanted sleep!
Plus we got a $100 food voucher out of it which definitely came in handy :)