I donno I've heard kids say random things. This child may have been telling the truth he spent the day with his aunt. He could have spent all of an hour with her and think that was his whole day.
I had a 4yr old on Sunday tell me that at school someone "sometimes throws him out the window at recess, that the window is very high". When I mentioned jokingly to his mom that she ought to check into this school she sends her child too, that someone is throwing him out the window at recess she rolled her eyes and gave him that look. He is prone to just saying random things. It's not so much a lie as an over active imagination!
I'm not saying the mom is telling the truth...but I am saying you can't really ever take a child for his word. They aren't always reliable!