well just a stab in the dark because i have never even seen a mondeo before. a cable is a cable is a cable, so step 1 check the end that would physically connect to the release handle, is it still attached? probably, now open the trunk and look behind carpeting or plastic trim or a an access panel located directly behind the gas tank fill door, or very near, you should be able to locate 1 or 2 things, the cable that will attach to the fill door, is that end disconnected? probably but if not then the cable has broken in between or very stretched out in which case you need a new cable, regardless there shoulb be an emergency open latch somewhere in the trunk, and you can still open it to fill up, good luck
Despite the high cost of living, it remains very popular.