You'll have to ask CGTrader admin if it is possible for you to again download a model that you purchased, that the vendor has deleted. Many sites keep backup copies to help out purchasers in this way. Your odds are better if the vendor is still active on this site and has other models for sale at this time. But, please don't be disappointed if the original model and everything associated with it is truely gone from CGTrader. Especially if the vendor is also gone. At some point, storage costs make it prohibitive to keep everything that was every published.
But, you probably cannot leave a review for a model that is no long sold on CGTrader. When a vendor deletes a product, the product (and all references to it) are removed from the published database. So, the answer to this second question is likely to be "No."
