No, you are not storing the job itself, just a flag that indicates that the job was not done/or even stored. What's more, there really are various ways to handle failure of storing a job on a queue, but in most cases it's just the absence of the desired effect that can be a giveaway. Ie. you know that the job either didn't finish or wasn't even sent to the queue if it's effect (ie. updating the user's friend list from facebook) was not done.

Also, take a look at #5 for a great monitoring stats solution.