Warranties on cycling clothing in the event of a crash?
I don't think any manufacturer will give you any warranty in case of "abuse" of its products – and it surely could be considered abusive to have a crash with their clothing, even if it was sold as mountainbike clothing. There may be some exception with protective gear, but even then the manufacturer might argue that it was designed to get damaged or destroyed in order to protect you. In this case I could imagine the manufacturer might give you some discount on a replacement, as some helmet manufacturers do in case of a crashed helmet.

But for "normal" clothing, I don't think you will have great chances on such warranty.