He discovered three withdrawals, made on the same day, of $1000 each on a bank card which was meant to provide refunds to customers.
He called police, who found the money had been paid into three personal accounts belonging to Ms Tiller. She was charged with dishonestly using a document in August 2007.
Mr Chan allowed Ms Tiller to continue working for the company at Mr Alexander's urging, so she could repay the money she had stolen.
But Mr Chan remained concerned about the operation and decided to call in a private investigator.
He suspended Ms Tiller in December 2007 and tried to arrange a meeting with her, but when she did not reply he dismissed her in a letter in early January 2008.
ERA member Eleanor Robinson found the company had grounds to dismiss Ms Tiller but Mr Chan did not follow procedure. The ERA declined compensation, but found Ms Tiller was owed $3702.20 in unpaid wages and holiday pay.