Simple , just eat the salad minus the meat ,if any in the salad . By that time your friend would have noticed , that they forgot you are vegetarian and would as any good host would, offer you vegetarian food. In future , may i suggest that reminders to our good hosts are required, as its not easy hosting a food based party. Even for the professionals , ie those in the Food and Beverage industry such as Hotel Restaurants , they need to be reminded , seen one too many instances where the vegetarians needs are sidelined .