3 Children: 1 is approx 24. The other 2 are quite young and are into drama/theatre/music, not sports. Mum takes them to drama/theatre/music from what I can gather.If they owned a 2 million dollar house, it’s possible it’s large enough not to notice the comings and goings of other family members. Sams husband may have just assumed she’s come come home from her run as normal, cleaned up amd headed out to brunch without seeing her if it’s a large house or perhaps he was out gardening before the heat struck. They also have 3 kids that may have weekend sports etc that he may have been dropping them off at. and possibly everyone was just doing their own thing on the weekend. If they all work and have school during the week it’s easy to see that they may all just have their own things going on during the weekend and touch base with each other at different points of the day. JMO
House is large - but not that large to be unnoticed.