this morning, one user asked me that she entered a data (only one record,)on the database yesterday, but later she checked that is gone, I check the database, i am sure the data is now there. how do i retrieve the data back, or how do i know whehter this is user problem? Thanks in advance
Ask the user to show you how she decided that the data was missing. Watch carefully to see what she does, especially if it doesn't retrieve the data as expected.
Users often do things we don't expect, and draw conclusions that we wouldn't. Sometimes they are well-founded (and we need to change code), sometimes they are confused (and we need to better educate them).