Unfortunately, that's actually how most warranties work. It's not unreasonable that HTC would want you to send the phone so they can repair and or replace it. Hopefully you have a backup phone you can activate in the meantime, otherwise if you want it repaired through warranty, you have to send it to HTC.
Your other recourse, is to go through your insurance. But that one will cost you money as you have to file a claim.
I started having the same issue a few days ago. There is a way to restore the phone. Just press and hold the screen just to the left of the volume control buttons, push the power button and wait until the icon lights on the lower part go out. Push the power button again, and most of the time the screen comes back fine. Sometimes it takes a few tries though.
That being said, the fact that Sprint won't address this issue is ridiculous. I took my phone to a Sprint repair center today and they looked at it for 1.5 minutes and told me to contact HTC.
I didn't buy the phone from HTC, I brought it from Sprint. I expect the retailer to stand behind the products they carry. If it had been a reasonably long period of time, I might accept Sprint referring me to HTC, but I've had the phone less than two months.
I've been with Sprint for over 15 years, I've always had any issue addressed immediately. This recent behavior by them has left a bad taste in mouth and I'll be leaving Sprint shortly. This is horrible customer service.
Keep in mind, while a recall would be great, it has to come from the manufacturer. I would suggest, every single time you, and everyone else using this phone, have an issue that you contact HTC at the following. The more people that report issues, the more likely something will happen. But In the case of Sprint, all they can do is keep replacing it as they aren't the manufacturer.
They have both an email link and a Live Chat where you can explain the problem.
I've contacted HTC, and they suggest that I either send the phone back to them, and wait for 7-10 days, or approach Sprint for a replacement.
Again I ask, Why is Sprint not standing behind this product? This is a "Sprint Exclusive" device that seems to be fundamentally flawed. It would seem that they might want to make sure that any problem s with their device is addressed. Instead, at least in my case, they are deflecting the issue.
Purchased the HTC Bolt 23 Nov 2016, less then 30 days the screen blacked out. I did not drop it or did it get into any water. Went to a Sprint Store and got it replaced with another HTC Bolt. Round 2 and less then 30 days- Half the screen went black. Today went to Sprint store and with my insurance plan will get another phone in the mail. Was told by the store manager if it happens again will switch out the phone with another Brand, may go back to LG.