Ooo you tried "štruklji", nice! This is my favorite traditional Slovenian dish, I eat it at least once every 2 weeks because it freezes well and it's quick to cook. Of course the ones from the supermarket fridge are not as good as home-made ones made from scratch, but still pretty good! I prefer the salty/savoury ones, the sweet ones are not my thing.
I think what that guy was trying to tell you at the food market is about the event called "Odprta kuhna
https://www.odprtakuhna.si/en/" which happens every Friday from June til Oct at that location. It's a pop-up food market where restaurants from all over Slovenia come (all kinds of cuisine, not just Slo) and have food and drink stalls there. It's a really cool event and super popular. The sustainability part that he was trying to explain (I think) is that there's no plastic allowed (cups, etc everything is paper or glass) and any food that's left is donated to charity.
Oh and the situation with the code, haha, very common with small hotels/inns where they don't have 24/7 reception, and I've heard such stories before with forgotten codes, main door keys etc before. Glad it turned out well though.
Glad you had a good time here!