For 16 keep checking mall on left side, brown door, I forget the day or time. For 20 I got it by going to storeroom on Wednesday in the afternoon.
I don't know if this is changed in the update or if it's possible to miss galleries, but I've been to the left side of the mall every time of every day and spam clicked on the entire wall with no result.
EDIT: found it, had to go on a date first, got the alert for "note in laptop" which tells me that it's available now.