The redemption update topic will give you this state change
Will give you the update when a redemption changes states
You should have the user token on file from the initial registration from the user, since they have to auth in order for you to be able to eventsub in the first place.
At time of writing to read/write channel point redemptions from the API you need a user token.
Feature requests to change this behaviour can be filed at the uservoice
https://twitch.uservoice.com/forums/310213-developers
But your use case is odd, since you should have a user token handy to use.
Since a user token is used to mark a redemption as complete too via the API. (Not just for checking status)
So not sure why you don’t have a user token handy in this example.