I found this BUG while trying to use MATCH using Queried data against the actual data.
This Google Spreadsheet shows the BUG in action.
When you format the data as Number the problem is fixed on row 5, but remains on row 2.
When increasing the decimal places the problem on row 2 surfaces as a precision problem.
Workaround use the FILTER function instead of QUERY. (Also shown in the sample spreadsheet)