Did they vanish over the winter or during the growing season? I had a couple of clematis vanish over the winter, but they were planted in a low-lying area in amended clay. I suspect they rotted in the waterlogged soil :(

Rabbits ate mine for years - left no trace - I finally protected them with chicken wire - 12" high cylindrical protection ( they like shaded feet so you can conceal the wire with ground covers/flowers. I only stuck it into the ground 1-2" they don't seem to dig under. Now my Clematis are all thriving. Good Luck

My jackmani disappeared this spring after I pruned it to 12 inches. I do have rabbits in that area, one of the few in the yard where I haven't seen vole holes. OK, so tomorrow I'll try to protect the rest with chicken wire.

I now plant all clematis in cylinders of hardware cloth, either the black plastic or the galvanized wire with 1/4” openings. My voles really like clematis and if unprotected the clematis often struggle even if not outright killed. I mostly bury the cylinder, but leave a couple of inches above ground. I make them from 36” wide hardwear cloth which makes a ring about 11” diameter, and I typically make them about 8” tall. I overlap the edges and wire them together.

This photo has a photo and a bit more detail.

I don’t have rabbits or deer that bother the garden, so I don’t have to worry about above ground protection.

kitasel, Never give up hope! I have had two clematis disappear; one was a white one, came with the house, not sure of name which I transplanted to another location in 2002, and one was a Piilu which I planted in 2011. Both disappeared after 1 season. This year, they both returned!