All case filings will be accessible via PACER. My own login has expired after several years of disuse, but it's easy enough to get one. It's all public record. As to how the USFWS realized Dayton was impersonating one of their officers, it wouldn't have to have come from a tip. If you do a reverse Google image search on that photo, you get both the actual officer and Dayton's TrekBBS posts.