For anyone else who comes across this solution when trying to search for repeater sub-fields:
Note that due to changes in WordPress, you can no longer use the percent sign as your wildcard. The percent sign will be substituted with a hash and your query will come up empty. So, see http://www.advancedcustomfields.com/resources/query-posts-custom-fields/ for a related example, which suggests using the dollar sign instead.
Since the dollar sign is used to indicate variable names in php, though, and can therefore cause confusion if you’re using a text editor with syntax highlighting, I prefer to use a string like XYZ for the substitution instead.
