I think that maybe there could be some sort of subtle way of teaching the player they can interact with the drawers.
Ignoring the object interaction silhouettes for a moment (which in all honesty, I may have just missed for the drawers on my first play through), I felt as though it was made apparent to me that you could interact with the lights and radios through the events of them turning on/off on their own which led me to investigate them. For example here are a couple of experiences I had while playing:
- The radio begins giving off white noise, I think "that's a creepy noise" approach the radio to investigate it. At that point I start trying to interact with the radio and learn you can turn them on and off. The fact that it changes states gives me an indication that I might be able to do something with it.
- I grab the key in the rightmost hallway and when I turn around, all the lights all turn off. I think "Wait, the lights can go out? It's really dark and spooky now, I want the light back!" It's here I realize the lights can be toggled on and off as I try to interact with lamp next to me that just turned off. As with the radio, the fact that something about the lights change, gives me incentive to examine them further.
Perhaps if you had some event where some drawers opened on their own, it would call attention to the player that they can be opened and prompt the player to look in the drawers as well without directly telling them to look in drawers.