I have noticed in latest JDeveloper 11g release, LOV components present in Query Criteria are not validated by default. In order to make it work correctly, you need to change attribute property in View Object.
Here I'm describing how to validate LOV components in Query Criteria. Download sample application - LOVQueryValidation.zip.
By default, if you enable LOV's in Query Criteria, there is no validation applied. For example, if to type values not available in LOV list and press Tab button to navigate out of LOV, invalid value is accepted and LOV popup is not raised:
Definitely you can notice that auto submit action is not done - its why validation is not invoked. In order to make it work, open View Object and for those attributes defined as LOV components:
Open Control Hints section and change Auto Submit property to true:
Now LOV validation works for both - String type attributes:
And Number type: