The required anti-forgery form field __RequestVerificationToken is not present

Im getting this error

<b> Exception Details: </b>System.Web.Mvc.HttpAntiForgeryException: The required anti-forgery form field "__RequestVerificationToken" is not present.<br><br>

Im using typeahead.js to autocomplete in a text box, but the action method on the controller never gets hit. Ive also used the typeahead.js for mvc 5 models helper. Heres my markup in the view

@Html.AutocompleteFor(model => model.NewUser.End_User_Org, model => model.NewUser.End_User_Org, "GetOrganisations", "User", false, new { htmlAttributes = new { @class = "form-control" } })

this is inside a form where ive declared

@Html.AntiForgeryToken()

and my controller action

[HttpGet]
[ActionName("GetOrganisations")]
[ValidateAntiForgeryToken]
public ActionResult Get(string search)
{
JsonResult result = new JsonResult();
if (!string.IsNullOrEmpty(search))
{
GetOrganisationRequestNonPrimary request = new GetOrganisationRequestNonPrimary(search);
result.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
var organisations = this._organisationService.OrganisationAutoComplete(request);
result.Data = organisations.Organisations.AsQueryable();
result.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
}

return result;
}

at runtime Ive checked the html and I have this

so the antiforgery token is present but why isnt it being sent to the controller action ? Is this a known issue with Typeahead.js and the mvc5 model helpers ?