I feel sorry personally that you didn't have a good stay as all our other guests did. May I humbly suggest few points below, which may make your future trips happier?
1. when you told us that you will be back at around 3pm, and you decided to come back 1hr earlier. The first thing you do, simply text message the host, via Airbnb. I was within 5min walk away as I knew that you will be back around 3pm, and also was confident that you have the wifi access. So even if you are at the door, text the host, let the host know you are here. This will save you from the emotion disarster and waiting time.
2. when the host tries to explain to you and comfort you down, please give him/her a chance. Especially, in our case, do not slam the door close next time when she just poured you a cup of nicely chilled water and put down nicely on the table in your room, and also was trying to talk to you.
3. If you want to talk, do not hestitate, as the host won't guess whether you want your own space not been touched, or you want to talk about the issue, or that you need some help. In our case, our schedules are almost totally different. We couldn't tell if you were in the room or not.
In one word, communication is one of the most important tools in our life. Keep mind open and talk to others, you will get benefits and have more fun in your trip!
One more thing, we open bnb for helping guests around to enjoy Singapore. That's why we allow guests to keep their luggage here when they arrive early or leave late. To be honest, I was quite shocked when you expressed that you thought we were stealing your luggages. However, I figured that out very fast as I understand that it might be your first time travelling alone and you were probably panic then. Giving trust to strangers is difficult, we are all on our way learning how. We also all learn from our experiences, sometimes bad ones.
Enjoy your trips!