How much pressure would amnesia add to your gospel presentation?

Over the last few months my small group has been doing a study on evangelism, which triggered a tremendous research proposal.

As far as I can tell, no one has seriously looked into the effects of amnesia upon faith.

Do those who loose their memory also “forget” the gospel?

If so, what would this mean for hardcore Calvinists? Assuming the assurance of election and salvation, this would surely mean that those who were authentically saved, even after their brain injury, would again accept the gospel if/when it was presented to them.

But, imagine the pressure...

You know, in the past, that someone with memory loss has accepted the gospel. Now, you’re going to present it again... 

What if they’re not convinced this time?

Frankly, I would feel like an absolute failure. 

Could you, potentially, tell the person that they have believed this in the past, or would you just start anew? 

Would the first technique be manipulative? 

Would you be extra watchful on their reaction, genuinely knowing, that this is the first time they had heard the story of Jesus?

Christian, or otherwise, I haven’t been able to find any data on the faith retention of amnesia sufferers, but I would be very interested...