I would like to add the following information for reference. Let’s say R1 queries R2 for a missing router. R2 will only query its neighbors if it previously knew about the requested route.
This is very important, because it doesn’t do so if e.g. R2 received a summary route from R1 and R1 queries for a specific route contained in this summary route. This gets important when we talk about EIRP traffic engineering etc.
I hope this helps.