How long does a Suggestion last, after the spell is over, in the NPCs head? [duplicate]

I’m aware that the Suggestion spell could last up to 8 hours or until the task is performed. However, take this scenario as an example.

I’m running Curse of Strahd for my group. They just made it to Vallaki with Ismark and Ireena in tow. They walked through the town square, saw Izek with guards, and comically went over to him to ask questions. Shortly into the awkward conversation, Izek noticed Ireena and immediately wanted to take her away for "questioning." The wizard in the group then cast Suggestion and told Izek, "There’s no need to take her." Izek failed his save so he agreed and went about his business replacing the old posters.

This is an interesting scenario for me because Suggestion worked but the wizard didn’t word it in a way that would last long (in my opinion). So at what point in time would it dawn on Izek that Ireena is in town and that he should arrest her? Would he need to see her again?

I have an idea in my head how this is going to play out but wanted others’ take on it. Thanks!