It could be your office clothes and you didnt look or smell like you Just be patient it will all work out. Misa when he was new growled and flattened ears back and prepared for a full blown attack when he saw me in an aussie hat and reckon he had bad probs in the past with someone in a hat.
Do you smell different ... had you been to the petrol station, used different hand cream, different soap, touched another cat? There is a strong chance you just didn't smell like "mummy" which is why he hissed.
You shouldnt go to work, quick quit your job!