Spot what’s missing…
No prizes but there’s 3 things in total 
Attachments
Yes I know it needs a clean lol
is the shock to the rear of the swingarm or front ?
I’ll go for two pads and the retaining pin.
your tyres are cheap (nilehcim) michelin copies
3 screws to hold the brake pads/calipers in place (2 on top 1 on bottom)
Did i win? What did i win?
How?!
Surely the rust and dirt would have held the pads in!
1 pad 1 bolt 1 pair clean underwear …is the missing items
One pad, one pin and the little plug that locks the pin?
Zeppo you’re correct.
Cue near brown trouser moment approaching roundabout and went to use rear brake and nothing.
I’m a bit sceptical they came loose as I used loctite on the screwable plug that fits over the retaining pins but at the same time find it weird someone would remove the pin, I mean if it was a deliberate act then why not the front brake??
Fortunately front brake is working well and a happy ending!
Shocks are to rear of swingarm
Ok i wont comment on tyre rotation being wrong then …
If I was a gambling man I’d wager you didn’t use Loctite 271 someone was after a cheap set of pads. Having extracted one and seen the state of it they decided a new set of Brenta’s from Wemoto might be a better idea. That or you need to invest in a torque wrench since you’ve clearly failed the nipping test 
I 'd not bother with a thread lock on brakes since breaking the lock which you must do from time to time can put undue, and unseen, stress on the shanks and threads. A smear of copper grease on the back of the pads, red teflon brake grease on the shanks of the retaining pins, another smear of copper grease on all the threads, torque to spec (or, perfect the art of nipping) and your good to go and go.
With regards to art of nipping I normally go hand tight + another quarter turn, will be investing in a torque wrench but still seems odd that two separate mechanisms came loose
Should there be a spilt pin / R clip to the brake pin
To stop just such a thing happening
Is that yer work bike?? The NHS must be worse off than anyone thought 
Haha no that’s my commute/hack, work bikes immaculate!
No it just screws in, doesn’t have a hole in it and doesn’t clear the hole to be able to drill and fit one
so the real answer was: a torque wrench, MOAR loctite, and ACF30