I would say there was nothing inherently harmful with the activity you were doing, you just overextended yourself and your back wasn’t ready for the work you were demanding out of it. You were fatigued and either form broke down or the demand on the low back was too high. You’re certainly correct in that losing a couple days or weeks of training is not the path you want to go down. McGill is a good place to start and breath work is very helpful. You want to reintroduce gentle movement to the spine without aggravating symptoms. You may have already seen the video, but Kelly recently posted a great video discussing this: https://www.youtube.com/watch?v=SO33_Nhl2Wk
As there are no red flags, I wouldn’t get too caught up in the precise diagnosis. Even with imaging they often show issues that may or may not actually be the origin of your pain and pain does not always mean there was damage. Even something very minor in the back can cause severe pain.
In the meantime you still may find that it helps to desensitize to movement and avoid any stiffness with smashing the area and some incorporated breath work. You have to find anything you can do that is not super irritating and start getting to work. Hammer technique work and try incorporating some hinging and squatting patterns to tolerance but avoid flexed positions which are aggravating. This is also a good time to incorporate some farmer carries or sled work and then build from there. Good luck!