Once you close the image the autorecovery file is deleted.
Auto recovery is of limited use IMHO. I have only once tried to use it since it was introduced, and was unable to. Premiere Pro has a much more robust recovery feature that saves multiple copies of a project over time, but PremPro references clips leaving them on your drives, so the saved files are tiny compared to Photoshop. All the same, it would be nice to have the option.
But, for the effort you'd put into setting up Auto-Save, you might just as well use a proper safe workflow and hit Ctrl (Cmd) s every five minutes.
[EDIT] BTW It might have worked if you'd stepped back a history state or two after saving the PDF file, or at least, giving PS plenty of time to sort itself out.
There's a multi-step "gotcha" sequence involving saving a PDF file that ultimately can cause the [ ] Layers option to be unchecked by default in your Save As dialog box.
In short, it did what you told it to, but you didn't notice [ ] Layers option had become unchecked.
Make sure when you save any PSD after saving a PDF that the [ ] Layers option gets turned back on.