You know, if your friend also uses Modo and worked on layers in ZBrush (or had stored a morph target before starting work without layers) you can actually salvage this with minimal effort.

 

Simply export the morph and export the non-morphed head (both from ZBrush). Go into Modo. Load in the non-morphed head from ZBrush. Then go Vertex Map> Background Morph Tool. Under the Lists tab for the object find the Morph Maps section and create a new morph map. Then import the morph from ZBrush. Click once in the viewport (you want to make sure the background morph tool reads 100% not more or less). Then hit the space bar to exit the Background morph tool. So now you have the morph stored in modo but you need to transfer it to a working head.

 

Import a working version of the head (one you know won't explode). If done correctly it should open in its own"scene". Then copy the mesh from the other scene (the one with the morph map) into the new scene as it's own mesh - if you use Modo, you'll get what I mean here.  Now for the fun part:

With your working head selected create a Morph Map for it. Then go Vertex Map>Transfer. A dialog box will appear and in the area called Source Vertex Map, choose the map for the morph you loaded from ZBrush (hopefully you gave it a name another than morph).  Voila. You have transfered the morph! Easy.

Now to get it out of Modo, you need to create another morph map for the working head and then go Vertex Map>Apply Morph. This will activate the morph in a way that it can be exported (otherwise, you'll just export the base not the morph).  Then Go File>Export. Done deal.

You can read Luxology's official explanation of the process here:

http://docs.luxology.com/modo/601/help/pages/modotoolbox/Vmaps/TransferVmap.html

 

Anyway, just thought I'd pass that on for any modo users who run into this issue. It's one way to salvage a bad situation. It's not always 100%  - it works best if the two base meshes are similar and positoned in the same place within 3D space. Also it helps if the base head the bad morph was generated from is still intact. Otherwise, you probably wouldn't be able to do this. I guess you could also use ZBrush's projection but that can be hit or miss.