Sterling first puncture bah!...or is it?

[rafiki]

Sitting here on the patio this evening the OH says " has that bike got a puncture?" Ignoring the 'that bike' description of my pride and joy I looked and it does indeed have a flat    First one in 1961km 

First thing check the valve: the lock down nut is missing! How did that happen? I pumped up the tyres before my ride this morning. The pump doesn't have the nut captured inside and there is nothing on the tiles that we can find. Ah well, new tube in the morning before it gets too warm. She wants to know if I can claim for that on warranty