Enormous amounts of SPAM email is sent advertising alleged "penis enlargement" pills. Absolutely none of them have any scientific evidence to support their claims. Many in fact have been scientifically proven to do absolutely nothing.
In the (unlikely) event that a pill was developed that actually could increase penis size, it would be enormous news and would be heavily covered across all media outlets. The incredible amount of mass-media publicity given to Viagra (which only increases the likelihood of erection) is clear evidence of what happens whenever a genuine scientific breakthrough occurs.