I work from home sometimes and often get told by a colleague to 'enjoy my day off'.
My sister has just begun working from home every Friday and people keep calling it her 'day off'.
AIBU to find this annoying. It can be hard enough to convince managers that working from home does not mean that staff will be arsing around, doing housework, minding kids etc. People going around calling it a day off, telling you to enjoy it and so on really don't help the image of 'working from home'.