IMAGE tracking - OnTrackingLost

[Doomkyn]

Hello, is there a way to know when the tracking has been lost?
Right now I can add models to the view when I Track an image with ARTrackingImageDetectedEventData, but I don't know when the image has been lost, and cannot destroy the models I created.
So that lead to having multiple models in the view if I point sequentially at multiple targets.

Am I missing something?