Unmerging clips without 3rd party plugin.

I have just received a project from my assistant and he has merged everything. I changed the folder structure a bit and now I have to relink all the audio manually. Premiere won't help me there by auto-locating as it usually does. I suspect it's because of the merged clips.

How do I unmerge so that I can work with the original footage? I'd rather not pay for a 3rd party plugin.