That is what I tried:
var cb = $('#cb');
if (displayCB) {
cb.combobox('loadData', []);
cb.combobox('clear');
cb.hide();
} else {
cb.combobox('loadData', newData);
cb.show()
}
The cb.show() results in a "regular" select appearing to the left of the combobox.
The cb.hide() results in the combobox remaining.
One difference is instead of starting from a <input>, I'm starting with a <select>. The ComboBox usage examples show that as a valid way to do it.
Update: I just changed it to an <input> and I'm seeing the same thing - instead of a "regular" select to the left, I'm seeing a "regular" text input control.