Only generic branded Chinese bikes would it be nearly impossible for a claim to be filed under the warranty provisions and expect some sort of satisfaction. The Raleigh bike in question is not a generic brand, Raleigh of USA will in fact honor the warranty if it's deemed to fall under the warranty provisions for frame failure. Trek (as well as a slew of other brands) have a lot of their bikes made in China and they have no problems honoring the warranties, just as Raleigh will have no problems honoring their warranty.

The biggest problem with warranties is whether or not it can be proven that the frame failed due to workmanship and or materials. If there is any evidence contrary to that then they won't cover the frame.

Would be more concerned about a carbon frame not made in China nowadays, with the exception of a few high end manufactures, inc TREK high end, manufactures in China have the most experience of mass producing carbon bike frames and parts.

What you do get with a brand (ie Raleigh, Schwinn etc), is warranty, which you don't get if you buy direct from say ebay, where there is no brand, or if buying 2nd hand in most cases.

In the OP's case, warranty probably won't be an issue to consider, as the frame was used, so no warranty, if it is cost effective to repair vs just replace, the OP needs to research that

I live in a rural/suburban central california town, and there's a guy here who has inexpensively repaired many carbon frames using the patch method, without even the need for much bike disassembly.
Colorado must have a few such repair facilities, ask around.

I take it that the crashed bike's owner is not a Pro or even elite rider, so the weight penalty will not matter.

The consensus over the years is that most carbon repairs are easily stronger than the structure was before repair, owing to the fact that a lot of stiffness is added local to the damaged area.

So, for about the cost of just preparing the frame for shipment and later reassembling it, you could have the structure repaired in-situ and be done with it.

I've known concussion victims to seemingly be more accident-prone for a while, and it's especially bad when it results in re-injury. A lot of bike racers I've known discovered this the hard way.