How did investigators know this? What time do you have for the *advertiser censored* search? I don't recall that the time of the search was released. Did I miss that?
Though theoretically another person could have accessed the house between the hours of 8:00AM until 8:00PM. The alarm apparently was not activated and the security cameras were turned off, no?
Someone taking a nap a block away could have walked over and accessed the computer when Rebecca was out shopping with her sister. It sounded like Rebecca was very busy on the day prior to her death. It is not plausible that she sat around and played on the computer that day.
However, imo, it is more plausible that someone else close by and within a short walking distance could have accessed the computer. Also, the possibly of remote access occurred to me.
More plausible, imo, though is that some one with a lot of time on their hands between the hours of 8:00AM and 8:00PM and who was free to sit and watch Rebecca's comings and goings entered the house and accessed the computer. Imoo.