We had a lot of materials from our studies on our GMail account and they were all labeled with colourful tabs. Now someone has changed this labels to different subjects and now I cannot see the old messages because they somehow disappeared. Have they been removed or simply moved to some kind of archive?
Check the Recycle Bin. You can also try typing in the topic or parts of the content of the e-mail you are looking for. Unfortunately, I think that when changing the labels, the culprit has also deleted all the old messages.