You don't actually have to restore the entire snapshot if you just want a single file! ZFS mounts snapshots read-only in an extra hidden .zfs/snapshot directory that doesn't even show up in ls -a unless you set snapdir=visible on the dataset but you can copy files out of there.

For example, cp /path/to/dataset/mountpoint/.zfs/snapshot/<snapshot_name>/path/to/file ~/path/to/file