I'll tell you this from my experience. I have a Samsung galaxy s6 and I never dropped it into any water and even if I did it shouldn't be flooded with water becouse its water resistent.But somehow the power button stoped working and I took it to the place where I bought it, when they opened the phone they found the phone was corroded from the inside and had many droplets of water.Now this I dont know how it happened becouse like I said in never dropped it in water ....but I did take it in the shower multiple times, which might be the reason of why it got water inside.
Any ways moral of the story yes your phone could get damaged by steam.