Photoshop remembers the last 10 or so files you have opened... You can see those if you choose File - Open Recent. It will open a side menu with your recently edited files.
If the files you're looking for are no longer in that list, did you save them somewhere in particular? It's kind of up to you to pay attention to where you're storing your data on your computer.
You might be able to see the last folder you saved into by opening a new file, choosing File - Save As, then looking at the folder that the dialog opens into.
FYI, for the future you can configure it to remember more recent files (up to 30 as I recall) in the Preferences - File Handling dialog.
Thx Noel. I will configure it to recall 100 in the Preferences. I guess I will keep searching for the missing photos. They are here somewhere on my external hard drive. Uggg
Do a file search on the modified date.
@StationTwo, I dont know how to do that, yet. Also I just opened the files I did not retouch them yet. The root of my delima is that I dont know where the files are on my external hard drive. I am brainstorming on how to locate them. Thanks StationTwo.