Icahn's latest quarterly disclosures appeared to confirm eBay's timeline, since they did not show a stake in the company as of December 31, 2013.
Reuters reported a day after eBay announced Icahn's stake that the activist investor had taken a larger stake of close to 2 percent, according to a source.
The confidence in eBay's shares suggests that key investors see further gains. The company's stock price rose 7.6 percent in 2013 and is up 7.4 percent so far this year. The stock price jumped as much as 12 percent after it reported better-than-expected earnings and Icahn's stake on January 22.
Not all hedge funds showed their love for eBay in the fourth quarter. Eric Mindich's Eton Park Capital Management cut its position in the company by more than 2 million shares in the fourth quarter, still leaving the stake at a sizeable 2.4 million shares, according to the regulatory filings with the U.S. Securities and Exchange Commission, known as 13Fs.
Ebay was not the only stock that Icahn and others agreed on in the fourth quarter. Icahn, who announced a "large position" in Apple Inc via Twitter in mid-August, found kindred spirits in activist investor Daniel Loeb and Blue Ridge, both of whom opened new positions in the company.
Loeb's Third Point hedge fund took a stake of 100,000 shares in Apple, while Blue Ridge took a new position of 320,000 shares. David Tepper's Appaloosa Management was an exception, cutting its stake by 12 percent to 215,320 shares.
For his part, Icahn's stake of 4.7 million shares at the end of December showed that he did not buy any shares of the company between October 24 and the end of last year.
In a letter to Apple Chief Executive Tim Cook made public on October 24, Icahn revealed that he owned 4,730,739 shares in the company as of that morning, the same amount disclosed in the regulatory filing for the period ended December 31.
In late January, however, Icahn tweeted that he had bought another half-billion dollars of Apple stock, boosting the value of his stake in the company to more than $4 billion.
Icahn waged a public campaign to get Apple to return more cash to shareholders but said earlier this week in a letter to shareholders that he was ditching his non-binding proposal to force Apple to add another $50 billion to its stock buyback plan.
He cited the company's recent repurchases as well as influential proxy advisory firm Institutional Shareholder Services Inc's call against his proposal.
Icahn's latest regulatory filings also showed that he owned 60.8 million shares of Nuance Communications, marking a 15.9 percent increase from his stake in the third quarter. Nuance makes the software that runs the Siri feature on Apple's iPhones.
Icahn did not show a stake in car rental company Hertz Global Holdings Inc in his fourth-quarter regulatory filings. CNBC television reported on January 3 that the investor had acquired between 30 million and 40 million shares in the company, which sent its shares up about 1.7 percent.