It sounds like you probably have a SmartLightng automation called Front Door which is causing the sensor to trigger the light.
Since this probably runs locally, it doesn’t show up in all the cloud account logs. (Only SmartLighting and a little bit of SHM are currently eligible to run locally.)
Open the SmartThings mobile app.
Tap the My Home icon (four little square on the bottom row)
Now find your light and tap on its name (not the icon to the left of the name, the name itself). This will open the thing detail screen.
Now if you tap on Recently you’ll see the individual device log.
But more relevantly, tap on SmartApps at the top,right of the light’s detail screen to see the smartapps that this light has been assigned to. I’ll bet you’ll see a SmartLights automation there.