If you represented the entirety of the percussion section, then you WERE the percussion section and would be correctly billed as 'percussionist'.
If you shared tasks with another percussionist (and they choose to address you individually) then it would be customary to call you out by your primary instrument (Snare, Concert Bass, Tympani, Triangle, Mallets, ...).
Of the course the Zendrum is a different beast, but I think you were right to claim 'Percussionist'. There are always some wankers that would have thought 'Zendrum' to be less dignified, and of course that think of a 'drummer' as an uncouth, inferior, sub-species of 'Percussionist'.
Always take the snooty high-road, I says.