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). Workers will often contact the Requester and ask for compensation for their work.
Researchers are encouraged to follow up with the workers and open a special HIT specifically for them by adding their Amazon Worker ID to the Included Workers field when designing their study. See the TurkPrime blog for more details (http://blog.turkprime.com/2015/05/longitudinal-and-follow-up-surveys-on.html)
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 set the linked URL to any legal URL and just notify the workers to ignore it)Sadly, Amazon Mechanical Turk does not provide a mechanism to pay workers who were unable to submit their assignments.