I recently left a job after 6 months. The gave me a relo package but forgot to have me read and sign the policy.

These are difficult situations. In other cases, some courts have held such policies to be unenforceable even though the employee assented to a policy, because the policy was not disclosed in detail to the employee. In other cases, since the employee was on notice of the existence of the policy, the employee was deemed to have agreed to the policy. You don't "need" to do anything. If you do nothing, they will either sue you or they won't. If they don't, then you're all set. If they do, then you can hire an attorney to defend you. In the meanwhile, you can continue to insist that you were not on notice of the terms of the policy and shouldn't be bound by it. This is obviously not legal advice.