When sending an individual email to thank a donor by using the email address link in their journal, the email will not pick up the 'payment route' field. The solution is to do a mass email, which is much more time consuming as it requires more steps in a different area of etapestry, and creating a querie. 

Logic says that if I can tailor emails for send individually, I should be able to include that particular mail merge option, I can see no reason why this shouldn't be possible.