When typing a search query into the search box located in the upper right hand corner of the "Plugins" window accessible from [Tools > Plugins] the search query fails to find all instances of text. This, as far as I can tell, occurs when the text submitted is located after "Source:". 
I have categorized this as P2 because a workaround may exist but it's impractical
because the work around would be to look at every plugin individually to see were the source of the plugin. This is more impractical to do in the Installed Tab as I was trying to gather all portal installed plugins to uninstall ones that I no longer needed or did not wish to have however when attempting to search "plugin portal" none showed up. I would have though that it might have been an excluded feature except the search would catch parts of the label (such as "plu") before the full query was typed.