What happened

Shares of driverless-truck start-up TuSimple Holdings (TSP) were trading sharply higher on Thursday in a dramatic rebound following a sell-off that may have been triggered by a short-seller's report.

As of 11:45 a.m. EDT, TuSimple's shares were up about 15.6% from Wednesday's closing price. 

So what

TuSimple, founded in 2015, is a San Diego-based developer of autonomous-driving systems for heavy trucks. The company has an impressive list of partners and investors, including big-rig maker Navistar International, United Parcel Service, Nvidia, and the heavy-truck unit of global auto giant Volkswagen. 

TuSimple drew another prominent investor shortly after its initial public offering in April: ARK Invest CEO Cathie Wood, who began adding shares right after the IPO and has added over a million more shares since the beginning of August. One of Wood's big buys (almost 295,000 shares) came on Aug. 12, a day after short-seller Grizzly Research released a report calling TuSimple "all smoke and mirrors."

A technician checks a lidar unit on an International semi truck fitted with TuSimple's driverless system.

Navistar, maker of this International semi, is a key partner of and investor in TuSimple. Image source: TuSimple.

I think Thursday's big gain was simply a rebound in investor interest, perhaps sparked by Wood's buying.

Now what

What about that short-seller's report? To my eyes, Grizzly's report on TuSimple is pretty thin, nothing like the in-depth reports that led to abrupt CEO departures at Nikola and Lordstown Motors. 

Among the "allegations," such as they are: An investor in TuSimple is also a key investor in Nikola, TuSimple's founders had an earlier start-up that didn't succeed, and TuSimple has "China origins" and is therefore (somehow) exposed to the country's recent crackdown on consumer-facing online businesses. 

Long story short: If you liked TuSimple a month ago, I'm not seeing any reason for you to change your mind now.