The question is confusing.
How can the Robot work on an item that has been already worked before, since it won't be in PENDING state ?
> The status would have changed to Success/Exception mostly.
If you are worried about adding the same Item again in Queue, then :
> Use Is Item In Queue action in Work Queue VBO
This action will take Key input and let you know if an Item with that Key is already present in the Queue.
Based on the True/False value of output you can decide to either add the Item in Queue or not add the item in Queue.