There's very strict quarantine rules here, but they're there for a good reason and the common-sense approach is not to bring anything that's organic, not that the detergent sounds like it was, though...
http://www.daff.gov.au/content/publications.cfm?Category=Australian%20Quarantine%20fixand%20Inspection%20Service&ObjectID=91BEA21E-F661-4C28-993E5D87CAB8AF20#declareI'm not seeing detergents in that list, but in the cruise review they did say that the question they'd been asked was if they had any detergents or toiletries in unmarked bottles, so my guess is that it was probably in an unmarked bottle and that's what caused its demise. Kind of sucks, but that's life. At least it wasn't anything expensive. Customs has a feel-good bit of PR on the telly right now that shows their work at international airports and if you think the Woolite was bad, spare a thought for the Australian woman who went overseas complete with shell jewellry she'd bought in Australia. They pulled her up on her return and insisted on receipts for the jewellry proving she'd bought it here, and when she couldn't they confiscated them and she had to pay a shitload of money for them to fumigate them and post them to her...