Don't know why people still giving suggestions I think they never go through whole thread as OP already got his money back on 11th July, 2008. http://forums.digitalpoint.com/showpost.php?p=8468911&postcount=14 DON.
Their ATM's balance sheet won't add up right when they open the machine... if you didn't get your $100 the machine should have an extra $100 not accounted for.. explain that you didn't get a receipt and they'll run the check.. if it comes out that there is an extra $100 they'll have you sign a paper saying that you have collected the money that hadn't withdrawn correctly and they'll put that in their receipt file for their balance sheets.. Its only a hundred dollars.. however, fight it on principal and win!!!!!!!!