Etiquette when packages are left with neighbors

Basically, a close friend of mine from Taiwan sent me a surprise package (full of Taiwanese snacks, of course :D) and since I didn't know it was coming, DHL left it with someone else in my building. With the way my building is set up, it's not necessarily my immediate neighbor, it could be someone downstairs or upstairs. I'm a Masters student and for the next few days, I will be at the university until later at night working on some group projects, so I won't be here during any appropriate time to ring their bell (imo; I'm either here early in the morning or late at night, not appropriate timing to ring the bell.)

Would it be okay for me to slip a note in their mailbox asking for them to leave the boxes in front of my door whenever it's convenient for them? I feel that some people wouldn't want to do this, in case it gets taken, but it's only in sight of the few people who live in my floor, which are two ladies in their 70's-80's who don't leave that often.

Also, is it normal to leave something like a chocolate bar with the note as a token of appreciation? They accepted a large Ikea package for me once before but I didn't have anything to give them at that time.

Thanks! :)