That sentence is incorrect. Should be: I remember meeting you at the mall.

As Charlie has said, your example is simply a mistake — it’s just a typo. That said, note that you will often see two “prepositions” together when the first one is an adverbial particle completing the first phrase, and the second one is a preposition beginning the following phrase. For example: “Don’t give up on your dreams” or “He logged in in record time”.

We hardly, if ever, use two prepositions one after the other. The sentence is incorrect. We have what we call prepositions of place and these explain when it is appropriate to use 'at or in' at a given time and in different scenarios.

Meet requires direct object without a preposition - meet somebody

In fact I don't think you read it in a book; you read it here in a post (quiz) yesterday on iTalki, where somebody made a mistake (a 'typo'). This was later pointed out and corrected...