You clearly have never programed an indexing bot.I don't know, blogs using autoblog plugins have been known to get deindexed. Googlebot doesn't need to actively "search" for the plugin every time it visits a wordpress site - just a manual culling of the footprint from hq is all it takes.
Googlebot would need to actively search by name to find a wordpress plugin directory... And of course you COULD rename that directory if you were paranoid.
"A manual culling of the footprint" is on the same plane as "Unicorns shooting rainbows out their asses" with something that simply posts blog posts.
Most autoblog plugins that were caught did something stupid like try to take credit for their work. (i.e. run an affiliate program for the autoblog plugin and force a link to it on their blog...)
That kind of footprint a 5-year old can find. But no indexing bot could spot this kind of thing without adding unacceptable search functionality.