The difference between partitiony types freebsd and freebsd-ufs is very important, as _martin pointed out. Using BSD disklabel(8) is very oldschool, discouraged & I strongly ask you thus you should try to remember the hardest you can if you had done that.
IIRC you can change the partion type with
EDIT when you changed the partition type to freebsd-ufs, you should be able to fsck(8) that partition.
IIRC you can change the partion type with
gpart modify -i index -t type
EDIT when you changed the partition type to freebsd-ufs, you should be able to fsck(8) that partition.