The issue is that Windows Search will, by default, only search through indexed files and AppData is, by default, excluded from indexing.
To change Indexing Options to include Appdata:
1. Go to Settings and search for "Indexing Options". This dialog will appear:
2. Click the "Modify" button at the bottom of the dialog. This dialog will pop-up:
3. Click the "Users" line at the bottom, which shows that the Appdata directory for your own user and the Public user are not searched. Once you do this, the upper part of the dialog will change to get you to Users, which you then hit the dropdown arrow next to to see your list of users:
Once you've opened the dropdown for the user for whom you wish to include Appdata in the search, check the box next to Appdata. If you want this for the Public user you will need to do this for Public as well.
Once indexing has completed on Appdata, which should happen very quickly, your Appdata files are now included in the search.
Another option, particularly if you like to search by filename as many of us "old-timers" do, is to use the Search Everything program from Voidtools. I love this program far more than Windows Search when I'm not looking to search on file or archive contents, which is the vast majority of the time. I've been using it for years and it's behaving just like it always did on Win10.
Brian AKA Bri the Tech Guy (website in my user profile) - Windows 10 Home, 64-Bit, Version 1809, Build 17763
Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.
~ Mark Twain