I've noticed that occasionally there will be an item posted in the Marketplace but it will be listed as "unavailable".  Is this a temporary designation? I would assume that if it were no longer available at all... ever, the item would no longer be listed.

Just wondering.

Sometime a product will be listed as unavailable which means the product can no longer be purchased, however it can be downloaded again if previously purchased. Please let me know if that doesn't make sense or if you have any other questons. 

It does.  In this case, I found out, it turns out the vendor removed it from Renderosity and is selling it over at Daz instead.