well jd,
at least they were prompt in getting another truck out for you to use, you said they used the term 'loaner', lets just hope they actually mean loaner because most companies i know of these days don't loan anymore, they rent. If its a true 'loaner' then that's a plus for you.
As for repairing those cards on Toyota's? i'm not familiar with anyone that does card repairs other than flight systems and whether or not they can repair these? i just cant say. There is a strong chance they don't utilize a repair program and will just replace it with a new one, if i were you i would make it a point to ask them that question specifically when you speak to the service manager.

Now i will say this, in my experience dealing with electric trucks, sometimes strange things do happen and this could just be one of those scenarios where the card may be faulty as a "new" card, it does happen unfortunatly, and if that is the case then it would fall under a "parts warranty" for the faulty card. So lets just hope thats all it was.

And my strong comments about that tech i said before may have been premature but it still makes me wonder that since he diagnosed the steering card as the problem to begin with why couldnt he go through the same troubleshooting proccedures again to verify if that one was faulty as well? or even the incorrect card? Or just simply troubleshoot the other problems that popped up and narrow the cause down. Or even called in another tech to come there and help him with the problem before hauling the truck in.
Its just puzzling and makes one think he may not be suitably trained for that level of diagnosis and repair work.

If it had been me? i would have exhausted every possible avenue before sending it in to the shop. But thats just me i guess. :o)