I find it suspicious that the set of the most common symbols doesn't contain a dick. Why wouldn't the most common modern wall ornament (in my experience) be popular at that time?
You guessed wrong. Of course I heard and saw the figurine in museums with my own eyes. What's your point?
Is there a vulva too - no not yet RTFA.
People were probably not talking (or telling stories) about their dicks that much, as opposed to something like "man and woman".
While the symbol may not be very useful for telling stories I think it should still be pretty common because it could be used for "artistic expression", demonstration of dominance, a joke or vandalism.
In the tomb of Ti at Saqqara, in a mural depicting a battle, there is a hieroglyph comprising a stylised phallus entering an even more stylised vulva. It is an insult that one warrior is hurling at his enemy. Apparently it is usually translated, somewhat primly, as "Come here, you copulator"; in his Scorn: With Added Vitriol (a collection of invective across the ages), Matthew Parris prefers the earthier "Come 'ere, you fucker."
That article deserves its own thread. TIL instead of using red lights Roman brothels just carved a dick in the ground to point the way.