My dog has been brought up with a cage since a puppy, she's never been told off andtold to go to it, I work many hours through the week, she goes in her cage from 7-1 in the day then I am at home to let her out in my dinner hour, she is then left in it again from 2 til 5 when daughter comes...
I most certainly would contact them, that could have caused an injury if you hadn't noticed.
I've found large stones in mine before, didn't do anything about it though, but you might get a free bag or a discount off your next bale