This isn't a problem with DomQuery, but with your query - the selectValue method returns the contents of the element or attribute that is selected by the query. In your case, it will try to return the contents of an input tag, which is always empty.
Instead, you want to select the value, something like this:
or in Java
DomQuery.selectValue(queryToElement + "/@value", parent)
Additionally, when selecting by ID, there is no need to use the id attribute, as DomQuery supports most CSS selectors - you could instead say just
There is no need for a parent, since ID attributes in HTML must be unique across the document, and the browser has built in mechanisms to search for an element by a specific ID.