I was looking for the same thing then I finally find a solution that seems simple.

Quick answer:

I use history.action value to determine if the user is coming from a back button or from a classic navigation. If history.action is equal to 'POP' then the back button has been hit. Otherwise it's 'PUSH'.

Detailed answer:

I get access to history in props of each page because I do something like that:

<Provider store = { store }>
    <AppRouter />
</Provider>

Where AppRouter is:

import React from 'react';
import { Router, Route, Switch } from 'react-router-dom';
import createHistory from 'history/createBrowserHistory';
import PublicRoute from './PublicRoute';
import PageHome from '../pages/front/home/PageHome';

export const history = createHistory();

const AppRouter = () => (
    <Router history={ history }>
        <div>
            <Switch>
                <PublicRoute
                    exact = { true }
                    path = "/"
                    component = { PageHome }
                    history={ history }
                />
                < ..... Other routes here ..... >
            </Switch>
        </div>
    </Router>
);

export default AppRouter;

And PublicRoute component is something like that:

import React from 'react';
import { Route } from 'react-router-dom';
import Header from '../components/header/Header';

const PublicRoute = ( { component: Component, ...rest } ) => (
    <Route
        component={ ( props ) => (
            <div>
                <Header />
                <Component { ...props } />
            </div>
        )}
        { ...rest }
    />
);

export default PublicRoute;

In React Router, the component stays mounted if router calls for paths that are children of that component. So, in your example, you can do something like the following:

<Route path="items" component={Results}>
    <Route path=":id" component={Detail} />
</Route>

This way, Results component does not get unmounted when Detail component is being mounted because Detail is a child of Results. However, if you do not want to see Results component getting rendered when you are in Detail, you can only render children when they exist. Something like the following:

 class Results extends React.Component {

     render() {
         if (this.props.children) {
             // This will enter Detail component
             return this.props.children;
         }
         return (
             // Render results component
         );
     }
 }