The workflows around Mobile Form generally involve rendering a form in the browser and then capture data and submit it back to the server. You cannot render the form if you are not connected to the server. In general, data capture step doesn’t need any connectivity from server except in case of running any script on server side or executing a web service. But connectivity is very critical in case of form submission. If you are not connected to the server and you submit the form, you would get just 404 error page and you data would be lost.
Generally, the solution is to check connectivity before one submits the form. Mobile Form with ES4 Sp1, brings out this check out of the box. It will first issue a HEAD request to LiveCycle Server to check if it is still accessible. If this check fails, it will show the following dialog. Once it gets assurance then Mobile Form submits the data to the server.