In the scenario below one should be able to access the defined UserData value in the SearchCompleted event handler

How to reproduce:
protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            this.radMap1.ShowSearchBar = true;
            BingRestMapProvider bingProvider = this.radMap1.Providers[0] as BingRestMapProvider;
            this.radMap1.MapElement.SearchBarElement.SearchProvider = bingProvider;

            this.radMap1.MapElement.SearchBarElement.SearchProvider.SearchCompleted += BingProvider_SearchCompleted;
        }

        private void BingProvider_SearchCompleted(object sender, SearchCompletedEventArgs e)
        {
            Telerik.WinControls.UI.Map.RectangleG allPoints = new Telerik.WinControls.UI.Map.RectangleG(double.MinValue, double.MaxValue, double.MaxValue, double.MinValue);
            this.radMap1.Layers["Pins"].Clear();
            foreach (Telerik.WinControls.UI.Map.Bing.Location location in e.Locations)
            {
                Telerik.WinControls.UI.Map.PointG point = new Telerik.WinControls.UI.Map.PointG(location.Point.Coordinates[0], location.Point.Coordinates[1]);
                MapPin pin = new MapPin(point);
                pin.Size = new System.Drawing.Size(20, 40);
                pin.BackColor = Color.Red;
                pin.ToolTipText = location.Address.FormattedAddress;
                this.radMap1.MapElement.Layers["Pins"].Add(pin);
                allPoints.North = Math.Max(allPoints.North, point.Latitude);
                allPoints.South = Math.Min(allPoints.South, point.Latitude);
                allPoints.West = Math.Min(allPoints.West, point.Longitude);
                allPoints.East = Math.Max(allPoints.East, point.Longitude);
            }
            if (e.Locations.Length > 0)
            {
                if (e.Locations.Length == 1)
                {
                    this.radMap1.BringIntoView(new Telerik.WinControls.UI.Map.PointG(e.Locations[0].Point.Coordinates[0], e.Locations[0].Point.Coordinates[1]));
                }
                else
                {
                    this.radMap1.MapElement.BringIntoView(allPoints);
                    this.radMap1.Zoom(this.radMap1.MapElement.ZoomLevel - 1);
                }
            }
            else
            {
                RadMessageBox.Show("No result found for the provided search query!");
            }
        }

        Telerik.WinControls.UI.Map.Bing.SearchRequest request;
        private void radButton1_Click(object sender, EventArgs e)
        {
            Telerik.WinControls.UI.MapLayer pinsLayer = new MapLayer("Pins");
            this.radMap1.Layers.Add(pinsLayer);

            request = new SearchRequest();
            request.Query = "San Marino";
            request.SearchOptions.Count = 10;
            request.SearchOptions.QueryParse = true;
            request.UserData = "Tooltip";
            BingRestMapProvider bingProvider = this.radMap1.Providers[0] as BingRestMapProvider;
            bingProvider.SearchAsync(request);
        }

Workaround:  if possible cache the data to be accessed at a later stage