DD, Dh and myself all had a nasty bug which manifested as a grotty cold for 7-10 days, a day or two of vomiting and diahorrea (sp?!) and then a further week or two of cold.
The sickness wasn't a sicky bug as such - it was all part of the cold. Dr even agreed that it wasn't a stomach bug. Maybe your DS has something similar. (Unless you'd prefer to have the day off, in which case, phone in! )