First of all, what does "SELECT @@version" report?
Next what do you get from this query:
SELECT * FROM sys.query_store_plan WHERE last_force_failure_reason <> 0
You said you removed the plan, but the only place I can find last_force_failure_reason is in sys.query_store_plan. So, one of these things must have happened:
- The failure occurred again.
- You removed a different plan.
What is a little tricky with plan forcing is that the actually plan may be a different plan, one which is "morally equivalent" to the original plan. This can lead to some confusion.