Recently I backed up my db and restored to another environment. There was an issue with some persistent subscriptions where Pinned strategy is selected. They were stuck until I change the strategy to round robin. How should we deal with this scenario, because we do not have the old consumer anymore, - how should new events of existing stream be handled with Pinned strategy then?
Your persistent subscription resumed because you updated your persistent subscription settings, not because you changed the strategy per se. It forces a checkpoint.
Expect more features around persistent subscriptions later but in the meantime, enabling stats on persistent subscriptions and setting up an alert on your monitoring system when a subscription got stalled is a good practice. When triggered, your alert could replay parked messages for example.