I thought they always showed up on a CRB, as I got one when a louche young woman, and when I did my teacher training was told this was the case. Three CRB checks later, for my three teaching jobs, and having declared said caution, and in the cautions and misdemeanours bit "none recorded".
Because of this, last CRB I asked my head, and he said to cross the box saying "no" to "do you have any etc". Then got a letter to school and phone call asking me to prove my identity via finger prints, as someone with my name and details had come up on the system. Spoke to a woman at CRB, explained circs of my (in my view unjustified arrest, after which I made a complaint about an officer with the Met). She basically confirmed that yes, what I had told her tallied with her screen.
Then, about a fortnight later, my new CRB arrived. "None recorded". What's going on???