In jQuery documentation it says:
The matching text can appear directly within the selected element, in any of that element's descendants, or a combination
Therefore it is not enough that you use :contains() selector, you also need to check if the text you search for is the direct content of the element you are targeting for, something like that:
function findElementByText(text) {
var jSpot = $("b:contains(" + text + ")")
.filter(function() { return $(this).children().length === 0;})
.parent(); // because you asked the parent of that element
return jSpot;
}