At this point, no explanation is required. Here is the testing conducted at Wimbledon 2009 for the qualifying, men's singles & doubles, and women's singles & doubles draws. No surprises. All the tests were conducted on match losers (or withdrawals) with the exception of champions. The only complication is that in a few instances a player had multiple matches on the same day, so I couldn't pin down exactly the match for which the test was conducted. However, the rules still held, so it wasn't an issue. Let me know if you find any errors.
As always, my data sources are provided below for those who want to verify my results and for those who don't want to believe their eyes.
Players tested and test dates: ITF's 2009 Anti-Doping Programme Statistics
Win/loss and Round Info #1: Wikipedia
Win/loss and Round Info #2: Tennis Explorer