To answer your enquiries I got a call from my local friendly bank-teller yesterday with the conclusion to the Great ATM saga!
'Tracy' has counted the ATM, (twice) to discover that it Balanced. Yup. No excess $300. No refund for wee Stephie and a VERY LUCKY DAY for someone in Daylesford around 4:30 on Saturday.
Oh well, no Karma Cash Cow for me then! I'm considering it as a 'Very Random Act of Kindness' on my part, hopefully whoever is $300 richer really needed it!