When we landed in Munich, Germany, a Hertz representative told us our reservation had been canceled. After some delay, checking on his computer and his garage, he assured us that we could obtain another smaller car. He said it would cost slightly less than our original rental amount, but that we would have to take up the refund of the original reservation with Auto Europe.
My husband signed a new charge slip (of course, all in German) and we were glad to finally be on our way. The Hertz agent only gave us a credit card receipt, but no rental agreement.
While still in Europe, my husband sent an email to AutoEurope, letting it know about the cancellation. We returned the car without incident.