I took the battery out of the phone for a few minutes and restarted my phone. The phone turned on normally except the screen wouldn't turn on. I called myself from my landline and used the normal gesture to answer my phone and confirmed that I'm able to receive phone calls and that touch controls are working. I also tried booting my phone into both the recovery and ODIN download screens. I'm not sure if I successfully booted into those modes, but I do know that my screen didn't turn on when I tried to boot into those modes.
I took the SD card out of my phone and activated my backup phone through the Sprint website. I tried resetting my SPH-L710 after deactivating it, and the screen was functioning again. I reactivated my SPH-L710, and now it appears to be functioning normally. I have no idea whether taking the SD card out or deactivating my phone actually solved my problem or if it was just coincidence.
My ROM is MD4 with root. I have Team Win Recovery Project v126.96.36.199. My phone has been nagging me to install 4.3 for a few months now, but I haven't gotten around to researching updated ROMs yet.
My phone now appears to be functioning normally. Has anybody experienced anything like this before?