The first known use of the heart-shape for love is a 1250s French manuscript, the Roman de la poire, a lover offering his vaguely pine-cone heart to his lady. Earlier candidates: Cyrene's coins stamped the silphium seed, a heart-shaped, now-extinct fennel traded as contraceptive and medicine, making the city wealthy; ivy and peepal leaves; Galen's pine-cone description of the organ. Hearts were drawn upside down until the fifteenth century, when the modern orientation and the playing-card suit arrived. It became a verb in 1977: I love NY, glyph and all.
Saint Margaret Mary Alacoque's 1673 vision of the Sacred Heart is sometimes credited as the origin, but the shape was centuries old by then; the vision's flood of images just baptized an existing icon. Valentine's industrialization did the rest: love notes, Victorian cards, video-game health bars, and the modern like button, a heart you click, affection as metric, the silphium city's descendants selling the seed again.
The claim: the heart symbol proves icons need no accuracy, only availability, the true organ was too ugly to love, so culture minted a prettier fiction, and every icon since, the cloud, the folder, the phone handset, is the same: a shape we agreed on because the real thing would not fit on a coin. Verdict: the documented drift supports it. Symbols are not pictures of things; they are treaties about things. The heart we send is not the heart we have. Everyone signs anyway.
If the symbol is a plant, a pear, or a bottom, why did nobody pick the actual heart?