Also in the example you can see the cached result is undefined.
angular
.module('app', []);
.run(function($templateCache, $injector) {
var compare = angular.injector(["ng"]) === $injector
//alert(compare); // false is the correct answer in this case. you created an new injector that's not linked to the module.
$templateCache.put("something.html","You some actual content here!");
var cached = $templateCache.get("something.html");
alert(cached);
});