Lightmix disappeared

[ValeroStudio]

I ran 3 batch images and had them autosave as EXR. When I came in this AM, I spoke with the design team and we made a little change to the design. I loaded the EXRs into the VFB and rendered a region that would update the affected areas. Then I resaved the EXRs and also some flat JPEGs. We wanted to render out an option B so I tried to do this in the same manner but the VFB did not remember any of the adjustments I made and Lightmix was completely gone, like I didn't even have it in the VFB anymore even though I was rendering the Lightmix render element. I was testing this method as a workflow when these small edits come my way. Did I do something wrong? Are the adjustments and Lightmix not remembered when you render a region and then resave the EXR? Is this normal behavior? Seems to me we would want it to.