@mikelow
At the risk of repeating myself, there's a risk you're moving on from "researching" to catastrophising.
If you're thinking of mainly travelling in the UK, I think it's a safe bet that most people won't be aware of those types of lock. Unless the key is bright & noticeable, the chance of leaving it in a place, at the same time as such a joker, for a sufficient amount of time that they actually lock and throw away the key is miniscule.
A statistician could probably draw up a list of far more serious things that are more likely to happen!
If you're going to be travelling in Europe where those locks are more common, the "joke" has a whole lot less impact.
The simplest way to avoid key anxiety is to use combination locks.
One winter evening I pulled up outside a supermarket in the western suburbs of Rotterdam. A group of young lads were hanging around that made me a bit nervous. I avoided the normal bike parking area in favour of a bright streetlight opposite the door. With cold fingers I struggled to lock the bike. (It was my commuter too, so had a big, heavy chain lock).
Removed my handlebar bag and did my shopping, constantly nipping to the door to check the bike.
Eventually got back to the bike, the lads only a few meters away. There, on my rackbag was my gps and my phone - right where I'd left them!😊
I was mortified and felt more than a little guilty.
There are, of course, many sensible steps that can be taken and they vary depending on bike, load and location, covered here and elsewhere. However, there are probably hundreds if not thousands of reasons to not tour.
Once the "perfect" lock is in your possession, the danger is that you can't disembark until you have the perfect tent/gps/pillow......
Nothing wrong with being sensible, but I'd urge against thinking too much.
Or as someone smarter than me put it "Pack for your dreams, not your nightmares".
Good luck!
