I just downloaded a list of matches from FTDNA on the chromosome browser view so that I could sort the segments by chromosome and position. I saw that the list includes tiny segments, so I filtered to include only segments over 10cM before sorting. Googling how FTDNA determines matches, I see that whenever two people share a segment over 9cM they are considered a match (and sometimes even when the longest matching segment is shorter). Thus, every person in my filtered spreadsheet should be in the list of matches.
However, for quite a few of the listed names of my matches, when I search the surname in FTDNA no person shows as a match. There separation between the download and the search is just a few minutes, so these people aren't somehow removing their accounts in the intervening time.
What's going on here?