brightside turned off and won't charge or turn on

My Samsung Brightside was working without incident. I usually keep it turned off and without a battery, except for emergencies or to check for messages every few days. But after my neighbor had a car accident, I extended my offer to help their family if they needed anything and left a battery in it, and left the phone on all the time for a week, in case my neighbor texted. I walked over to check it in case I had a text message, and the screen was black. Figuring the battery was dead, I put a charged battery in the phone but it remained off and black screen. I plugged it into a wall charger and still nothing, no Verizon logo, no power, no symbol showing it was charging, no lights or sounds. I swapped out the battery for yet another battery and still nothing. I plugged it into a USB port on my computer and nothing. I can’t seem to get any data recovery programs to find the phone because it won’t turn on, even while on a charging source. I need to retrieve text messages from this phone. I was able to retrieve all photos as they were stored on the SD card. The phone was not dropped or exposed to temperature extremes or any water; it was just sitting on the counter and apparently died and no battery, charger cord or charging source has successfully revived it. Any suggestions?? If data recovery can’t find the phone, is it dead? Or could it just be the backlight of the screen that has gone black? Can that be replaced?