The home appears to be vacant.
She was not the listing agent so she would've been representing the buyer only. It is not unusual for a buyer's agent to call the listing agent directly and not go through the office to set up a showing, especially if they know each other and have worked deals in the past. It is also not unusual for the listing agent to say, "The home is vacant, show anytime, the lock code is....". In this situation (and even if she called the office and not the agent), she would not be required to give the potential buyer's name or info.
Some agents don't use the coded locks obtained through the real estate commission. It is common for some real estate agents to put a lock with their own code....a lockbox that can be bought at Lowe's or Home Depot. It this were the case, there will be no time stamp of when she entered the house.
I am hoping maybe this is all some crazy misunderstanding, or that she just needed some personal time away and staged her own disappearance. I hope she turns up well and safe regardless. Prayers for a happy ending.