The date and time of submission is reflected in the survey results, only if the survey is set to anonymous, then the date and time is not saved. This has a good reason, because based on the date and time of the answer, you might be able to break anonymity.
So: Is your survey anonymous?
Here is the screen you see when activating the survey with the options of setting responses to anonymous and also the option to include a datestamp (which will not be written to the database if the survey is set to anonymous - see second screenshot):
Here is the warning you get when you set your survey to anonymous when activating it:
Now, if your survey is not set to anonymous, but you did not set the options for the datestamp, you'll probably won't see the date/time the survey was submitted.
This can not be changed afterwards, as then this information was not stored.
[quote[How can I recover this info?[/quote]
In the tow cases above (survey set to anonymous or datestamp set to NO) you will not be able to recover this after the survey has been done. These settings should have been made before the start of the survey.