Hello and thanks for using Just Answer.
I am Al and am happy to assist you with your enquiry.
I would advise that you are perfectly ok NOT to mention this whatsoever.
The question is asking if you have had cause to complain or there is an issue which may deter the Buyer from proceeding- so, if the caravan was still there and it was causing a nuisance to you in some form, then you would need to disclose it. However, as you did not need to complain and the caravan is no longer there, there is absolutely nothing you need to disclose to your Buyer, in this regard.
I hope this puts your mind at rest, and sets out the legal position.
Can I assist you any further?