get a receipt from them for the work, detailing the accident, even if it has "no charge" at the end of it, and also on the understanding that it has an independant inspection by Triumph to make sure it is straight.
once the independant inspection is completed and satisfactory, inform the garage that you will then close the case, but not until then incase there is other damage not initially spotted when you pick it up, as they could say "well you took it away accepting its right, so you must have done it since"....
i expect it will be alright though, we fall off our offroaders all the time (they have much more spindley frames that a road bike and they dont bend the frames very easily. ive known a few road bikes have frontal impacts hard enough to bend the forks and the frames have survived ok, modern frames are an engineering masterpiece and absorb a lot of force (int he right plane!)..... so i should think youll be ok, but get an independant inspection done just incase as part of the deal.....
good luck.
