Okay, here goes nothing:

1) Download and unpack this ZIP file. This should create a folder named "pydeltamesh-main."

2) In Poser, select "Run Python Script..." from the File menu, navigate to the folder you have just created, then pick the subfolder named "pydeltamesh", and within that, the subfolder named "poser." There's a file named "fixVertexOrder.py," which is the one to run.

3) The script will now pop up a file chooser where you select the original OBJ file exported from Poser. After loading the file, it will pop up a second one where you select the morphed OBJ file exported from Blender or whichever modeler you used. It will then do some computations that could take less than a second or several minutes, depending on the mesh.

4) Once the script is done pondering the meshes, it will pop up a third file chooser in which you select the output file, again in OBJ format. I advice against overwriting one of the input files, in case your modeler messed up more than the vertex order or the script got confused by some other issue.

Hope that helps.

-- I'm not mad at you, just Westphalian.