@Cynthia814 I am sorry for what sounds like a disappointing and frustrating experience. If a host double books, whether an accident or an error on their part, if they are offering alternate accommodations they should be comparable. If they cannot, they should consider other solutions, such as a discount or the ability to cancel and receive a refund.
That being said, if you accepted the other property and stayed the entire duration without bringing forth your concerns, it might be difficult to acquire any form of refund at this point. In the future, if something ever arrises, such as this, make sure you document it through airbnb, whether on messenger or by calling. This gives you ground to stand on later if you do feel you are entitled to some form of compensation.
As for the review, I would leave one. Although you didn't have a direct experience staying on the property, you did have an experience. I would say something along the lines of "Upon our arrival we found the home already occupied as a result of a double booking. Unfortunately this resulted in us being moved to another accommodation, and we did not get to stay at this property." This is short and sweet but highlights the issue. Just a note though, I would be careful in stating that the alternate accommodation wasn't up to par, because if you didn't bring up these concerns to the host, they were not given the chance to rectify it, making it a bit unfair to mention.
Hope your airbnb experiences go better moving forward.