The guard will admit that they did receive the report a while ago but did not look into it further due to Ciri's decent reputation. But in needing to bring her into questioning further, they believe it is a good time to clear her record of suspicious activity if she believes it's in error.

Whether or not they have the power to do this for her is debatable but it is clear that they may be keeping information on the Summoned whether they speak to them directly or not.