What happened?TuSimple shares (NASDAQ:TSP), which creates self-driving technology to long-haul trucks, rose 8% Tuesday. This brings their two-day gain at 25.3%. Monday's jump of 16% was a record. This is the second consecutive day that the stock has reached a new high.The prospects for the newly-public company are exciting investors, as it held its initial public offer (IPO) in April 15. The stock was IPOed at $40 on Tuesday and closed at $70.55 by Tuesday. This means that it has risen 76.4% in the two-and-a half months since it first traded.The S&P 500 rose 0.6% in the first 2 days of the week.What are you waiting for?TuSimple did not release any news Monday or Tuesday. There were also no Wall Street analyst updates.It seems we can rule out the stock as one of the growing number of meme stocks -- stocks with high short interests that individuals investing in certain Reddit communities are flocking to.As of June 15, 2015, only 4.4% of TuSimple’s float (shares that are available for trading) was sold short and 2.9% of its total shares had been sold short. Even though trading volume was slightly higher than normal on Tuesday, it was not excessively high and Monday's volume was just about average.We can conclude that the 25 percent increase in TuSimple stock prices over the past two days was mainly due to a combination of individual investors buying shares and institutional buying, and more individuals discovering the company.It is worth noting NVIDIA (NASDAQ :NVDA), a tech giant, was a preIPO investor in TuSimple. Popular stock picker Cathiewood has also bought shares for a few of her ARK Invest exchange traded funds (ETFs).What now?As I concluded in my recent deep dive on TuSimple, I believe that TuSimple stock is worthy of a spot on growth investors' watchlists. This includes those who are comfortable investing in companies that aren’t yet profitable. The company is in an area with enormous growth potential, has many top tier investors and partners, and has substantial cash.
