How do I recover a previous version of a page layout?
I modified a page layout in our QA environment using Apex and didn't refresh from the server (my last refresh from the server was 10 days ago). Someone else made a TON of changes using the web interface in between then. I just overwrote all of her changes!
Does anyone have any advice on how I can undo my changes and go back to hers?
Unfortunately there's no tracking of layout changes so there's no way you can just revert this — are there any other developers who may have had a later copy of the metadata and haven't refreshed theirs yet?
It can be a good idea to use ANT to run a metadata backup system so that things like this don't cause problems :) There's a guide to using the Force.com Deployment Tool here, essentially you just want to use half of that process on a regular schedule.