Where can I find the OTA update file?

I'm trying to locate the zip file that contains the OTA update for my Droid Bionic. Right now, its failing to update, and every time it fails it deletes the file and I need to re-download it (takes a long time). I was hoping to save off the update so I could try a few things on my phone and try the update. I read online its somewhere in a /cache directory, however I dont see anything at all when I mount it to the PC and do a search for cache or even "*.zip". Does anyone know how I can find the zip file? Maybe I need to change the PC settings or something to search for it (I have changed the folder settings to view hidden files and system files).