I will investigate what is involved to add some style of functionality to track the last product viewed to the laston or iponline table which ever would be best. Should be an easy enough addition to simply record the ad viewed however note ads content is temporary so there would have to be alot of checks to ensure things exist before any such info would be shown. Which is why I question the feasibility of such a trivial addition.
I can look at creating some new sidebar pal for this in 5.3 Beta 4\
The checks that I see looking at the code are like this. The ipcache table does record the last product a user views. Now what we can do is create a box that displays the last viewed ad if it exists and if there is even a record that a user has viewed any ad only then would a result be shown.