So, I haven't been able to get the ID, but I was able to accomplish my end goal (which was filtering a list result based on the current user). I used this finally.
var userName = $().SPServices.SPGetCurrentUser({ fieldName: "Name" });
var query = '<Query>' +
'<Where>' +
'<Eq>' +
'<FieldRef Name="SharePointUser" />' +
'<Value Type="User">' + userName + '</Value>' +
'</Eq>' +
'</Where>' +
'</Query>';
$().SPServices({
operation: "GetListItems",
async: false,
listName: "UserAccessList",
CAMLViewFields: "<ViewFields><FieldRef Name='Title' /></ViewFields>",
CAMLQuery: query,
completefunc: function (xData, Status) {
$(xData.responseXML).SPFilterNode("z:row").each(function() {
// will return only results that match the current logged in user
// in the 'SharePointUser' column
console.log($(this).attr("ows_Title"));
});
}
});