Note: no need to use sudo when running coredumpctl.
Huh, that’s strange.
Assuming you have made no custom changes to your systemd-coredump configuration under /etc/systemd/coredump.conf or /etc/systemd/system.conf.d, then my only guess is your core dumps were deleted because systemd-coredump is configured to keep 15% of your disk free by default, so core dumps will be deleted if you have less than 15% disk space remaining. Maybe your disk is pretty full?
If not, then have you made any configuration changes in /etc/systemd/coredump.conf or /etc/systemd/system.conf.d?
Also, please verify that you have not made any custom changes to your core limit: ulimit -c should print unlimited.