What to do when the monitor disappears from your study?

The case of an experienced contract monitor removing themselves from a study, not returning original documents and not completing any of the monitoring activities (such as monitoring reports).
In this particular case, the monitor did not invoice for the work and “disappeared”.  The sponsor made attempts to contact the monitor, sent a registered letter, but in the end there was no further communication.  One of the sponsor’s concerns was related to the subject safety with respect to the monitoring activities not having been completed.   So, what should a “quality” perspective be on something of this nature?
Although it may seem unusual it’s not, by any means.  CRAs come and go, whether they are independent contractors, CRO employees or even sponsor employees.  If you are in the business long enough, you will come across a few bad eggs.
In the above case, since no money was exchanged it is futile to try and retrieve anything from this person.  What there should be is evidence that you (sponsor or CRO) have pursued it with no success.  Document the attempts at contact, file them in the Trial Master File indicating how many sites had been affected and what CAPA you are putting in place to ensure that the site’s data had not been compromised.
Make a list of any original documents that have gone missing and are irretrievable.  If the CRA is part of a professional body such as ACRP, you may have the option to report it to that body’s professional conduct committee.  They may withdraw the membership, but it is not likely they will communicate the issue for others to know about since there may be intervening circumstances on the monitor’s end which could pose privacy issues if pursued further.
You will obviously need to re-monitor all the work, which will require significant resource if several subjects’ data are involved.  Allocate two or three monitors to the site for a couple of weeks (based on the number of subjects and visits – usually one day per subject will be needed at minimum) to get it done faster.
With respect to possible safety concerns, it is not the monitor that makes the call regarding a subject’s safety, and if there are safety issues these can and should be picked up in the database (most studies have Drug Safety Monitoring Boards that get statistical safety data for this very reason).  With the different options of monitoring these days, the onus of protecting the subjects is on the PI, so the sooner you can get out there to re-monitor the better, in case any serious events have not been reported.