Can’t offer any advice on how to get your money back but here are a some things I do to try and avoid this happening to me:-
1. After docking a bike, go to the terminal and select “Print Journey Receipt” – you don’t actually print one (I did end up with lots of paper at the beginning) – and make sure the journey I have just done is showing. If it is, it shows the system knows that you have returned the bike.
2. On the odd occasion it doesn’t show after a few attempts and having checked the bike is securely docked (system might be running slow or occasionally the terminal has lost data contact with the system) take a picture of the docked bike showing the serial number. Most phones nowadays will also date/time stamp the picture with location.
3. If in any doubt about whether the bike is logged back in call the call centre and tell them you are having problems. Start fixing any problem before it starts costing you money!
Hope you are successful in getting a refund.
Seems a bit odd since, if you hadn’t docked the bike correctly would expect the system to stop the clock next time the bike was used and returned.