I made a bit of a mess. After joining a large model to check for naked edges I opened a new file and out of habit I clicked ‘Yes’ when asked if I wanted to save the changes. I now have about 24,000 surfaces all in a single layer and I need to edit it. Without being able to hide various groups of surfaces this is proving to be difficult. Is there some way to recover the layer information?
Hmm - no, if the file has been closed and reopened I don’t see how to get that info back. I’d try opening the 3dmbak file of the same name in the same folder before saving this file again, that may have the state you want.