A voltstick wouldn't have helped in this case because the circuit was already known to be live, maybe an old type neon screwdriver would have alerted you but if it was water in the bottom that got tipped around internally when you grabbed it then it also might not have tested live before you moved it.
An RCD also isn't protection against shock, it doesn't even reduce the shock at all it only limits the duration. It's going to trip in 40mS but in that time you will still receive 4 pulses of over 300 Volts peak voltage which is way more than enough to put you on your a$$.
Working with gloves on would have helped to some degree. Something else that would help if you keep one hand in your pocket the old fashioned way is LV dielectric shoes to EN20345 sometimes called ESR or EH rated. They're not like the HV linesmans wellington type boots, they look like normal sneaker shoes and I'm not sure why these haven't caught on in the UK. Come to think of it I can't remember them ever even being mentioned on the forum. Might be time to add a pair to your wish list.
Electrical Insulated (1000volt) Safety Trainer
enduro.co.uk
Electrically Insulating technical footwear from Spanish brand Robusta TECHNICAL INFORMATION
sparksworkwear.com
za.rs-online.com