In other words: If you find a bug, you MUST do the following steps immediately:

• Record reproduction steps with selenium - or such - (for web projects)
• Write a note about the encounter
• Attach the selense file and the note to a bugreport in an issue tracker (you have one do you?)
• Try out other possibilities to recall the bug (or similar faults)

If you follow the steps above, it's almost good. Just don't forget to fix them before implementing any new features.