Unfortunately, there isn't a log where this information is written. The good news is that the new release of SAS Visual Analytics (7.1 - shipping this fall) will include what you are looking for right there in the UI.
In SAS Visual Analytics Administrator 7.1, the size of the table (in MB) is listed on the LASR Tables tab. The SAS LASR Anayltics Server has also added the ability to compress data when putting it into memory and VA Administrator and Visual Data Builder will both support that functionality in 7.1 as well.
There are some other cool features concerning memory management and governance coming in 7.1-- stay tuned for more details as we get closer to the release date.