Retail investors bought $7.3 billion in Tesla stock over the past two weeks, signaling a 'buy the dip' mentality as the stock plunges.Tesla insiders have sold a combined $335.2 million of stock since November, while retail investors continue to buy.Net retail buying of Tesla stock has been positive for 12 consecutive days, the highest magnitude in over a decade.Despite recent volatility, Tesla CEO Elon Musk urged employees to hold onto their stock, emphasizing the future value of autonomous driving.