How to recover my task?

When you accept any task, it tells you the time limit or deadline that you have to complete it. I did not do the toolbar task but I do a lot of the others. The time limit is generally between 2 and 8 hours... but perhaps for something like testing a toolbar it was different. In any case, if the task is now in your "completed" tab, your time limit expired without you submitting something. You cannot recover those tasks. If you don't do them, you lose them. The "abandoned" time, if I recall correctly, is not your time limit (your deadline is stated separately)... I believe "abandoned" is the amount of time the task/open spots stay in the system for people to accept them before that task disappears.