Any of the vapor lines disconnected with a tool may be damaged. The female connectors are easily damage by excessive force. As for what to do, you are on your own. The Ford service manual does not list the O-ring as a replaceable/serviceable part. Once when my Son and I replaced a fuel pump in a 2000 Ford Contour, I used a pair of neddle nose pliers to disconnect a vapor line. Big mistake. The O-ring came out and the fitting would not re-click. After multiple attempts to get the O-ring back into the groove, I gave up and got another set of vapor lines from the salvage yard. Lesson leaned. When the manual says, "do not use a tool to disconnect", there's a reason. Very painfull leason as this was the only home project I have every done where I called a tow truck out and took the car to a professional to complete the job. We simply could not get the correct angles without a lift (working from jack stands). It turned out that we had damaged the connector with the pliers and did not know it at the time. The design of the Mustang's tank is much better than a Contour's. What a nightmare the Contour was. When you find the leak/problem, can you take some pictures?