Issue
I want to know if users have deprovisioned my add-on from their apps but I don’t know how to check.
Resolution
If you’re using v3 of the Add-on Partner API, your add-on implementation should have received a deprovision request as described in this article: https://devcenter.heroku.com/articles/add-on-partner-api-reference#add-on-deprovision. See https://devcenter.heroku.com/articles/platform-api-reference#add-on-info for instructions on how to use the Platform API Add-on Info endpoint to get information about a specific add-on resource. If the endpoint returns a 404 error response, then you know your add-on was deprovisioned from that resource.
If you’re using v1 of the Add-on Partner API, your add-on implementation should have received a deprovision request as described in this article: https://devcenter.heroku.com/articles/legacy-add-on-partner-api-reference#deprovision. See https://devcenter.heroku.com/articles/add-on-app-info#get-app-info for instructions on how to use App Info API to get information about a specific add-on resource. If the endpoint returns a 404 error response, then you know your add-on was deprovisioned from that resource.