No Sample Requests are "found" in v12 ASM Traffic Learning

As boneyard indicates, a logging profile which logs either all requests or illegal requests locally should help you locate requests in Event Logs: Application Requests. If you see items in the request log, but not on the Traffic Learning screen, then you have a different problem. Go to Learning and Blocking settings, and verify if the violations you would like to track have the checkbox for "Learn" selected. If the Learn checkbox is not selected, then you will not see any learning suggestions on the Traffic Learning screen for those violations.