Data can go missing for several reasons:

• Sensors hold ~10 days of humidity and temperature data. If the data buffer fills up, the oldest data is deleted first.
• The sensor does not record data while the ¼” jack is plugged in.
• The sensor battery has died.
• If you are logged in to multiple phones, data is trapped on one of the phones if the app is not running or the phone does not have an internet connection.