Hi Dodgy Rider.
Do you mean just the trip, or is the odometer zeroed as well. I have had the Odometer reset. My bike is the 2004 model. From what i have heard, there was problem with that model and if the battery went flat then the odometer resets to zero (not every bike does this). There was over 7000 miles on my bike when it reset. Now it reads just over 1000 miles.
I have looked into this and there does not seem to be anyway to get the mileage put back on. Well unless you get your bike clocked.