It did not strike him that it was at his house. So it has to be someplace that is like his house.
For instance, it probably was not a log home or a home with lots of big windows or a home with lots of art work or a home with plaster walls or wood paneling, etc. There are a lot of differences in homes. Not every home looks like another inside.
However think about the last Snap you got - when it's just a pic with a message you tend to disregard the pic and read the message. If the message is - "hope you had a good day I love you" you just register that it was a positive or nice or happy message. If you are exhausted from working construction all day that may barely register. He said he can't remember what the snap said and isn't positive where she took the picture. Completely understandable and heartbreaking as I'm sure he can't stop trying to remember.