Perhaps there may have been a bit of misunderstanding on some of the posts on his thread. I am sure we all appreciate that failing to recall could in some cases cause real harm, including death, and we have high expectations of how it should work.
I don't think anybody is suggesting that the mock recall is limited to merely contacting the customer. All of the elements of recall must be challenged
ie
The ability to recognise a serious problem
Investigation
The availabilty of key managers their understanding of their roles and the quality of their decision making
The backwards and forwards traceability of materials from goods receiving to customer identification
Customer contact
Review
etc.
The initial query, as I understood, it was restricted to the method of communication with the customers, particularly if they do not respond readily. In a test, there has to be a limit as to how many times you attempt to contact the customer. In a real recall you should incorporate follow up contacts by phone, e mail, post or pigeon if necessary at an appropriate frequency until you get a response.
In a test you have to satisfy yourself that you have the ability to contact the customer(s) and the methods described in the thread can achieve this.
The test should be as challenging as possible, eg out of hours, removal of key players,choosing the less obvious materials.
Setting KPIs such as tme limits for the different stages is a good technique for initiating improvements in many areas of the operation.