workshop assessment form unclear about submission status

Some students thought they had submitted correctly the form but in fact they did not  because of some error during the submission (probably they did no fill a mandatory field). Is there a way to provide a simple message confirming the submission or clearly warning that there is an issue to avoid this kind of situations.

Probably this issue was aggravated by the fact that the students were using browsers in their cellphones to fill the workshop assessment forms, which gives little space for warnings.