nHibernate QueryCache NHibernate.ObjectNotFoundException: No row with the given identifier exists

Question

I encounter an exception during working with nHiberante hql query with query cache. I will try describe situation:

• nHibernate, QueryCache enabled

• HQL query with region, and cache set to lets say 2 hours

Records from table targeted by HQL query are read and stored in cache. After some time record in table are removed by plain SQL - not using application but using SQL IDE. nHibernate starts throwing exception (not immediately but probably after expiring 2h window):

NHibernate.ObjectNotFoundException: No row with the given identifier exists *Unique key of object that nHiberante is trying load from SQL db but is not present anymore*

I have couple of questions:

• how long nHibernate will try load such record? The same time as query cache region is set - 2h? It looks like nHiberante store key of loaded object and is trying reloading using it but if row is not present I'm assuming it should return null not missing record.
• Is only way to get out of impact by restarting application?
• Is there a "good" way to change nHiberante behavior and say that if there is no record in database return null instead of throwing exception?