[Sprint Samsung Galaxy S 4 Q&A, Help & Troubleshoot] fmrider:
Wow, you guys rock - learned my lesson the hard way on this one! I wanted to come back and summarize the issue and the steps to resolve in case anyone does what I did. I can't post links because my accounts too new but the steps are what's important.

Issue: Rooted Galaxy S4 but forgot to enable debugging and also left the phone encrypted

Symptom: After rooting, the phone would boot up to the first password entry for encryption, then the screen would go black but the phone would stay on.

Solution. First get some tools:

Get lastest version of Odin(Odin_v3.09_and_older.zip),

Then get the .tar file for the version Android you had installed (for me it was 4.3 file name SPR-L720VPUEMK2-20131212171424.zip or L720VPUEMK2_L720SPTEMK2_L720VPUEMK2_HOME.tar.md5).,

Then get a recovery (I used TWRP file name openrecovery-twrp-2.6.3.0-jfltespr.tar).

Download the Samsung USB Drivers (file name SAMSUNG_USB_Driver_for_Mobile_Phones.exe)

Now, first install the drivers. You should be able to go into the device manager and see that your phone connects if your drivers are installed correctly.

Next I tryed to install a recovery - this will give you the tools you need to wipe your encryption away and everything else. So open Odin, unselect auto-reboot, click the 'AP' button and navigated to the TWRP .tar file, boot your phone holding the volume down and power at the same time - this should get you to a screen asking you to press volume up to install a custom OS, or down to cancel. Press Volume up. Connect the USB cable (you should hear the audible 'ding' to tell you it is talking to the PC). Your Odin program should show that a Com port was connected (doesn't matter what COM port - for me it was sometimes COM3 or COM4). So you're connected, you have the .tar recovery file ready to go so press 'Start'. Hopefully at this point you should see it successfully install - if not you need to back up and find out why it won't program that recovery file.

Now that we have a recovery, you can turn the phone on holding the volume up button at the same time, when you see some small txt at the top on the same screen as the galaxy logo (sorry, forgot what it said - was 3 lines, multicolor) let go of the buttons and you should enter the recovery. I had to mess with the timing on this a few times to get in.

Once in TWRP recovery, I found the option to wipe everything (especially the internal memory).

I took my stock OS .tar file and put it on my SD card, reinstalled back into the phone. I rebooted the phone and it tried to load a recovery and it supposedly succeeded - proceed with caution here because for me I know from rooting other phones that this wasn't quite right but it worked.

So it seemed to load a recovery, then rebooted and got stuck at the Samsung galaxy screen. Also, I couldn't get back into my nice TWRP recovery. Holding volume up and power led me to a simple screen to either load from usb, sdcard, or reboot (couple other options to wipe cache and whatever). The important thing is that the encryption was wiped away at this point and I was able to talk to my phone through USB.

I tried loading my .tar file from this screen and it was a no go. So I went back to my trusty Odin. I loaded the stock 4.3 OS just like I did the recovery and it finally programmed!

The phone rebooted and everything was good to go. It was unrooted again and booted back up like it was new out of the box.

Sorry if this wasn't totally accurate but with enough trial and error you should get it. This took me around 8hrs of messing around, downloading files and scouring XDA.

Huge shout out to dewrust since he ultimately helped me here - he probably doesn't need the help, but there he is in the newb section giving advice - very generous.

Hope this helps someone else at some point in time.

fmrider