I had a guest for a week. After they left, the Eero app showed their device connected intermittently for several days. 
The first picture shows their average daily scans during the week they were here. The other three pictures show the following 3 days, when they shouldn’t have been here. 
Is it possible that the app is giving false positives? I realize its a dumb question. I’m trying to give them the benefit of the doubt, and just need confirmation either way. 
Thank you