Many people have reported that experience after ancestry purged the match list shortly before end of 2014. Some have been able to actually see where the dna matched and size on other sites with chromosome browsers.

In fairness, this has happened after each of the three big autosomal dna companies have revised their formula for reporting matches, but many people believe ancestry over purged using its so called pile-up application (eliminating matches in areas for individual people). Despite their white paper, there is a lot of mystery about what they did with matches that show up on other sites with significant dna matches visible on chromosome browser tools at the other sites and paper trails to common ancestors. Unless you transfer to another company or gedmatch, there is no way here to tell why those matches disappeared.