iPhone camera not working after Telugu bug?

The only documentation that I have seen from Apple states that the results of the Indian character were to apps that can use text, such as Messages, WhatsApp, etc. Nothing about the camera.

Only Apple could truly answer your question, however I would say it seems it wouldn't matter what the answer is considering what you have said about the other party. Up to you how to handle this, but older phones can display any variety of problems when things like this are introduced. However, I would have to say that if it were an iPhone 5c, it could not have been updated to iOS 11.2.6, which is what was released to fix the problem. So, since they have tossed the phone, it is hard for them to prove to you what caused the problem, as much as it is for you to say that it didn't. Kind of between a rock and a hard place here on how to deal with this, but I would say that some type of compromise is going to have to be struck. I would also say that your son has some responsibility since he sent the message. Not a good idea.

Because she is not tech-savvy and took it to a retail store instead of the Apple store, I am questioning whether it really was broken or whether the sales people were more than willing to sell her a new phone and contract rather than spend any more time trying to fix it. Argh!

My thoughts exactly, however I'm rather prejudice. I don't like Sprint at all!! Having them work on updates, etc., could have caused any number of issues. Any work should be handled by Apple, since it is their hardware and software. However, since there is no turning back at this point, you are going to have to decide what to do. I would counter that you are not responsible for the majority here since the phone is rather old to start with. The iPhone 5c and 5s were released in 2013, so the device is more than 4 years old, rather old in technology years.

This is just my personal view but would find it highly unlikely a “software” bug could cause a hardware fault, it might temporarily stop that component from working but following a Restore (ie. clean install of the iOS) all should be back to normal. Likewise for any Updates, I haven't known any to damage hardware, yes, something might not work due to corruption, but again a Restore usually resolves. You could give Apple a call (at an Apple Store) and ask there opinion though, just to get a second view on this.

But even if you can’t agree responsibly, if someone was asking me to pay for a replacement because of damage caused by a “disputed” action, I would first want to inspect the device to see how likely that could of been, and secondly if I agreed and paid-up I would want to retain said device for my trouble. I gather you have not been given the opertunity of either, which might start ringing alarm bells that all is not what it seems (ie. did the device show signs of excessive abuse, has it been dropped).

The above though needs to be tempered with how well you know the family, are they good friends of long standing or does you son want to retain there daughters friendship, in the end it’s a call I’m sorry to say only you can make.