Adverse possession in Virginia takes 15 years.

Talk to your neighbor even if you don’t like them.

Also, alert the fence company, there is probably a little plaque on the fence with their name and phone number. They are likely more sensitive to your concerns and should have had a survey or reliable plat before installing. If not, they’ll hade a document that their client assumed the liability of the location. Just don’t fucking threaten to sue the fence company from the start. Everyone says that and I see it all over Reddit as advice. I’ve never seen a follow-up post where someone was like, “holy shit y’all, it worked . . . I’m rich bitch!”