A shifter doesn't magically get pulled into spokes for no reason. It gets pulled into the spokes WHILE SHIFTING. If you were shifting to the largest cog, and the derailleur limit screws are off or the the hanger is bent then there is the possibility of the derailleur hitting the spokes and being pulled. This can only happen while shifting. Again you would have been in the second to last cog, shifted to the largest and then bang. All this would have happened at the same time, you would have noticed. Were you shifting when it happened?
In the end you have taken the bike to the Trek dealership and they are pushing for you which is good. There are other solutions but I wouldn't go there until I had to. Good luck, I hope it works out for you.