On occasion a worker may have completed a study but was unable to successfully submit the assignment for a variety of reasons (timeout, system hiccup, computer shutdown). In such cases researchers are encouraged to follow up with the workers and open a special HIT specifically for them.
This HIT would not have any real linked study since the workers already completed the work...it is just a method to compensate the workers for the work done. You can create this study by going to the "Design Survey" page and putting in a title ( e.g. "Compesation HIT" ), some dummy url (e.g. http://www.example.com) in the URL field, and paste the Workers you want to include in the "Include Workers with These WorkerIds". You should then Launch the HIT and send a link to the new HIT ("MTurk Preview" link ) in an email to all the Workers saying that they should just accept the new HIT and just submit it to get pad.
Sadly, Amazon Mechanical Turk does not provide a mechanism to pay workers who were unable to submit their assignments.