App uninstalled event (personal scope)

Hi there.
I'm trying to build a personal bot which has to send proactive messages regularly. I made it work by storing the conversation (and bunch of other field from the activity) when the user installed the app, just like the examples here. Now it works great, but I realized that I keep messaging users that have uninstalled my application. I can't find any event that is triggered when you uninstall an personal scoped bot (app).
I'm using the javascrip SDK if that's relevant. I'm open for any suggestions or different approaches on how to:
- remove stored conversations for users uninstalled the app

- do a check if the user has the app before sending the message

- anything else??

Thank you