It was the IPO that wasn’t: A biotech firm hit the market and traded for six days, only to announce Friday that it wasn’t issuing shares after all, thanks to a key investor’s failure to follow through on a commitment to buy stock. That meant all the investors who thought they had bought or sold shares in Vascular Biogenics Ltd. since it began trading hadn’t. The highly unusual cancellation of a deal days after the shares began trading is a black eye for lead underwriters Deutsche Bank AG and Wells Fargo & Co. and an unwanted headache for any buyer or seller of the stock. It also is a major setback for the money-losing biotechnology company, which had planned to use the proceeds of the $65 million offering to fund drug development. Vascular Biogenics, an Israeli drug-development company, said Friday that its underwriters at Deutsche Bank and Wells Fargo had voided the IPO. In a 104-word statement, the company said an unidentified, U.S.-based Vascular Biogenics shareholder didn’t pay for shares it had agreed to purchase.