I wouldn't make much of the 'abandoned' house owner not letting a load of people in his property to search for a woman who from his perspective he knew wasn't there. She was last was seen across the river, what would he have done if he was involved, wade across with her on his back in full view of anyone nearby? Maybe he was cantankerous or he took offence at how he was asked. The police seem to have searched the house now though and found nothing.
If the police really believe Nicola is just 'missing', not abducted, attacked or gone in the river, no mental or health issues that make her vulnerable (I think they would have said that by now). Why the massive search? She is entitled to go missing as an adult woman with all her faculties if she wants.
I wonder if her husband went down to look for her first when he was called or did he call the police straightaway before investigating himself? Was he at work or at home?
The police were asking for dashcam footage although obviously not of Nicola's car as they knew where it was?