Help! Newbie's tediously constructed LightRoom Classic hierarchical keyword list. vanished!

[autochthon]

Hopefully this is just a simple newbie user question with a simple answer:

I started to construct a hierarchical keyword list in Lightroom Classic, for my 2,500 photo collection. After about an hour, I had made great progress, and I needed to  create a new, top-level keyword, "date".  But because one of the keyword categories ("Last Name") was selected,  "Date" insisted on being created under Last Name: I couldn't figure out how do de-select the "Last Name" category  and there was no way to drag it out into the top level. 

So I closed the program (I saw no File/Save option, so I just chose "File\Close"). There was no "Save As" option after that; Classic just closed. 

When I re-launched Lightroom Classic, my newly organized keyword list was gone.

What am i missing....?

[dj_paige · Accepted solution]

One possibility is that you have accidentally opened the wrong catalog file. Use File->Open Recent and select each file shown there until you find the one with the keywords.

Off topic, but nevertheless, a hint: don't make dates into keywords. The Filter Bar allows you to search for an individual day, or several days, or an entire month, or several months, or an entire year. The functionality you need to search by dates is already in Lightroom Classic, without date keywords.