if you are using the Telerik Extensions for ASP.NET MVC - have a look at the following documentation on client side event handling of TabStrip
TabStrip Client API & Events
the way to select any Telerik Extension control from JavaScript is as follows:
View:
<%= Html.Telerik().TabStrip()
        .Name("TabStrip")
        .Items(items =>{/*items definition */})
%>
JavaScript:
<script type="text/javascript">
        function getTabStrip(){
            var tabStrip = $("#TabStrip").data("tTabStrip");
            return tabStrip;
        }
</script>
In your scenario in order to know which tab is selected, i would suggest you to listening to tabstrip select event and have a flag set as to which tabstrip is selected. Here is the code to handle client side events:
View:
<% 
  Html.Telerik().TabStrip()
  .Name("TabStrip")
  .Items(items =>{/*items definition */})
  .ClientEvents(events =>
    {
        events.OnSelect("Select");
        events.OnError("Error");
        events.OnContentLoad("ContentLoad");
        events.OnLoad(() =>
            {%>
                function(e) {
                /*TODO: actions when the control is loaded.*/
                // "this" is the tabstrip.
                }
            <%});
    })
  .Render(); %>
Javascript:
<script type="text/javascript">              
      function Select(e) {
              // "this" in this event handler will be the component.
              // the "e" is an object passed by the jQuery event trigger. 
      }
      function Error(e) {
        //code handling the error
      }
      function ContentLoad(e) {
        //code handling the content load
      }
</script>
As you can see you can set a flag as to which tab is selected in the Select() method and in your save button click check the flag and act accordingly
If you go through the documentation link i provided at top - it will tell you all the client side events and API exposed by the control
Hope this answers your question