Compensation! Typing on iPhone! 

You can re-add the journey, and add them again to your pass.

As long as you still have the trip and pass on the app you can retrieve the day’s ticket by using the day selection or calendar under “my pass”

To prove the delay I always take a screenshot of the timetable showing the delay when I travel on a delayed train. 

Update. I couldn’t add the trip including the London-Bruxelles leg but once I took that out I was able to add the Koln-Hamburg part which is where I was delayed. All sorted.    
 

I don’t seem to be able to re-add the trip. When I search for it in planner it says there are no trains available for that route on that day, 13th May.

Update: Have found the calendar but still can’t add the expired trip….Also I can’t find the calendar on my pass. Can you tell me where it is please. Thanks.

What do you mean by "can’t add the expired trip”? What happens at which exact step? Do you have a screenshot of any error or of where you get stuck?

As to a calendar in My Pass:

For a flexipass, you need to choose the travel day before tapping on Show ticket.

For a continuous pass, you first tap on Show ticket, and then you can change the sate at the top of the creen.