I think the fact that they have each other's numbers means that they've almost certainly encountered each other more than once.
Also, when I retired my last phone it had numbers on it for people I haven't seen or spoken to in well over 6 years. These days the idea of "keeping a person on speed dial" as something that implies meaning or a aspecial effor is a bit on an anachronism. Generally, you just accumulate numbers from various people and after a while it becomes more of a hassle to go in and delete all the unneeded ones.
Getting back to the episode though: yeah, I think it's perfectly reasonable for someone like Ollie to hold onto the contact number for the only person he knows who is 1) knowledgeable in the arcane arts and 2) owes him a favour.
Also, when I retired my last phone it had numbers on it for people I haven't seen or spoken to in well over 6 years. These days the idea of "keeping a person on speed dial" as something that implies meaning or a aspecial effor is a bit on an anachronism. Generally, you just accumulate numbers from various people and after a while it becomes more of a hassle to go in and delete all the unneeded ones.
Getting back to the episode though: yeah, I think it's perfectly reasonable for someone like Ollie to hold onto the contact number for the only person he knows who is 1) knowledgeable in the arcane arts and 2) owes him a favour.