Removed ppa: where have the packages gone?

I tried installing something to make a PlayStation 3 DualShock controller work on my Ubuntu 20.04 machine:

drubbels@drubbels:~$ sudo add-apt-repository ppa:falk-t-j/qtsixa
drubbels@drubbels:~$ sudo apt update
drubbels@drubbels:~$ sudo apt upgrade
drubbels@drubbels:~$ sudo apt install qtsixa

It did not make the controller work, unfortunately, so I chose to uninstall. I did not think to purge the qtsixa package before removing the repository:

drubbels@drubbels:~$ sudo add-apt-repository --remove ppa:falk-t-j/qtsixa 

I can no longer uninstall, or even find (using apt list --installed and dpkg --get-selections), qtsixa now (re-adding the repository does not make it reappear).

Was it removed along with the ppa? Or does it now exist invisibly on my machine as some kind of unfindable 'phantom' package?

If you have installed a package from a PPA, but then removed the PPA, I believe the files remain on the system. You can prove me right/wrong by executing the list statements below.

APT retrieves the packages and DPKG installs them. The packages themselves can be found on launchpad and you can see in the buildlog which files are included in the packages

https://launchpadlibrarian.net/194241587/buildlog_ubuntu-vivid-amd64.qtsixa_1.5.1+git20130130-0~vivid2_UPLOADING.txt.gz

Inside that buildlog, at the bottom, you will see lines that start with chroot which list all the files in the package

chroot-autobuild/build/buildd/sixad_1.5.1+git20130130-0~vivid2_amd64.deb:
drwxr-xr-x root/root         0 2015-01-07 14:18 ./var/lib/sixad/
-rwxr-xr-x root/root     26936 2015-01-07 14:18 ./usr/sbin/sixad-raw
-rwxr-xr-x root/root      6176 2015-01-07 14:18 ./usr/sbin/hidraw-dump
-rwxr-xr-x root/root     23048 2015-01-07 14:18 ./usr/sbin/sixad-bin

If qtsixa is still installed, you should have binaries starting with sixad in /usr/sbin and in /usr/share a directory with qtsixa

ls -la /usr/sbin/sixad*
ls -la /usr/share/qtsixa/

If none of these return anything, the application was removed. otherwise the buildlog contains all the file locations related to qtsixa.