"less" and "gpg" question

[ToddAndMargo]

Hi All,

I encrypted a file with
      gpg --symmetric foobar.txt

It created foobar.txt.gpg file as expected
and I DID NOT tell it to store the passphrase.

$ cat foobar.txt.gpg
clearly showed a binary file.

When I ran
    $less foobar.txt.gpg

it showed me the recovered file without encryption
and DID NOT ask me for a passphrase.

When I renamed the foobar.txt.gpg to foobar.txt
and ran "less" on it, now I get a binary file.
renaming it back to gpg and now it gets decrypted
again.

HOW DID LESS figure out my key and decrypt my file?

Are there are gpg keys stored somewhere"  How do
I whack (erase) them?

Many thanks,
-T