1. edit /etc/pve/lxc/100.conf or whatever number your container is. (or /etc/pve/qemu-server/100.conf for a vm)
2. find the line rootfs: usb_thin:vm-111-disk-0,size=16G.
3. edit usb_thin or whatever the dead drive was called to a storage pool that exists.
4. then pct destroy 100 works or in the Proxmox GUI destroy works too.
I guess just check that the new storage pool doesn’t have a disk with the same name, otherwise it may delete that disk.