Help .psd got flattened
I was working on one of my larger projects (I put 6 hours into it today, which is small for some but I'm not a designer by trade). I finish the project, get it signed off by my superiors, save it as a .psd on my desktop to be cataloged later. I go to mail the finalized product and it's too big on our internal mail servers so I open the .psd (layers still there), flatten it, and save it as .pdf (I don't save the .psd at all at this point). I close PS and all is right in the world. My superior calls me back 2 hours later and asks me to tweek positioning on a couple things and I say sure. I open the .psd and it's flattened! History is empty and I so I can't undo.
What happened? I never resaved the .psd! ! Is there any way to fix this without another 6 hours of work? Either way is there a way to stop this from happening again (over writing the .psd when I save it as a .pdf)?
