How to know if files are encrypted

Stupid question from a noob here:
I have installed Cryptomator. I have created a vault in Dropbox and placed a .txt file in there…
… In Cryptomator I have entered a password for the folder which contains that .txt file. I re-entered the password as requested.

While it is displayed as locked (viewing in Cryptomator), I go to my Dropbox (both through my own file-manager and through dropbox website). In both cases the .txt opens with no clue that it is encrypted. No request for password or any other clue. How do I know it really is encrypted?

If you can read the file name of the txt file, or it’s content within your Dropbox, then it is not encrypted.
The encrypted filename and it content is just a bunch of alphanumeric signs.

I guess you saved your Textfiles into your Lokal Dropbox folder and not into the new network drive that appears when you open your vault.

Here’s a setup description