I hadn’t restarted my serial logger after I rebooted my laptop, leaving me with no clue about what caused the crash.

Probably way too late now, but if it was a proper kernel panic, it should’ve saved the dmesg in the kernel’s pstore which saves to either ACPI or EFI storage (depending on BIOS or UEFI), which systemd then extracts to /var/lib/systemd/pstore/ on next reboot.