Your LimeSurvey version: 5.3.11
Own server or LimeSurvey hosting: (not sure where to get this information)
Survey theme/template: system default (the green one)
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Hi LimeSurvey community, 
 
We are using a very simple survey as a toy example to get familiar with LimeSurvey. The questionnaire lss is attached, which has only 2 pages – one is an introduction page and the other has 2 questions.  
 
As the screenshot shows, we sent out 6 survey invitations to our team, and we completed and submitted these interviews (“Total survey completed = 6”), but we got only 5 responses (“Full responses = 5” and “Incomplete responses = 0”); one respondent’s response is missing – it never shows up in the “Responses” page of the LimeSurvey system. 
 
We’ve tried several things but none of them work: 
1) checking “View saved but not submitted responses,” 
2) removing all filters in the “Responses” page (actually, no filter has ever been set up in this survey,)
3) exporting responses,
4) stopping the survey (making it expired.)   
 
Is there any other thing that we can do or check to get back the missing data?
Thank you very much.
 
 

could it be that this one missing survey was done by someone who was logged into the Limesurvey backend while filling out the survey?

I think I remember to have had cases where some responses were not recorded when I was logged into the LS backend while testing.

Thank you for the reply. That’s indeed a possible explanation. The missing interview was done by our teammate who created the survey, and she did fill out the questionnaire when she was logged into LimeSurvey Cloud. However, I remember that she completed more than one interview for that survey in the same condition (that is, she sent invitations to her different email accounts as if there had been several respondents, and she completed all the interviews while she was logged into LimeSurvey Cloud), but all the other responses of hers were recorded.

We’ll do some tests to see whether the problem occurs every time when someone fills out a survey while logged into LimeSurvey Cloud using the same email account, and see whether the problem may also occur when someone is logged in the system and filling out the survey using different email accounts. In any case, does LimeSurvey count that as a bug needed to be fixed later?

Well, it is just a suspicion of mine, because I think it happened to me before. And yes, it is not always the case. Sometimes they get recorded, sometimes they don't. But I can't really reproduce it, so I can't really make a bug report, because I am not 100% if it really is what I think it is. Just a suspicion, that it might have to do with this.

Because sometimes when I activate to test, some responses of mine are not recorded. Others are. So it is not all the time. This makes it difficult to identify the issue.

Thanks for your quick reply. Fortunately, the problem occurred when we were testing the system, and if you’re right about the cause of the problem, then it’s no big deal, because in a real survey, no respondent will be filling out a survey while being logged into the “Settings” page of that survey.

However, since we’re still unable to pinpoint the cause of the problem, and the problem occurred in such a simple survey, I’m a bit worried now. I’m quite new to LimeSurvey, so I would like to ask, in your experience, how often do you see missing responses in a real survey? Specifically, how often do you see in the “Summary” page that the number of survey completed is larger than the number of response returned?

In real life surveys I haven't had any issues yet, but then it is also easy that one or the other slips through, as you might not know who is answering. But from my experience it usually are issues during testing.