Custom HTML Values

Hello. I’m trying to add a field during checkout so that customers can tell us how they heard about our event. The HTML in the Checkout Note seems to work fine, but there’s no record of it in the sales details. Any idea what I’m doing wrong? The page in question is here.

This is the HTML in the Checkout Note.

<br>
<table style="width:90%">
  <tr>
    <td>
<label for="stageshow_amor_howtheyheard" style="display:table-cell">How did you hear about this event?</label>
<input type="text" name="stageshow_amor_howtheyheard" style="display:table-cell; width:100%"></td>
</tr>
</table>

Here is the relevant section in the JavaScript.

function stageshow_AddCustomHTMLValues()
{
	/* 
		Add values from custom HTML Elements here 
		Note: For multiple custom HTML Elements call stageshow_AddEntryToCheckout for each element
	*/
	stageshow_AddEntryToCheckout('stageshow_addtomaillist');
        stageshow_AddEntryToCheckout('stageshow_amor_howtheyheard');
}