Looking at other's card. It's ok?

[chadattak]

2 days ago I was playing cash games in a private club with 2 nl tables with semi-pro dealer. In one hand, I raised pre-flop and bet the flop and 4th street with TPTK against 2 opponents, 2 calling station at my right. Just before the dealer dealt the river, one of them took a peak again at his cards and I could see that he has hit trips.

So anyway they both check to me and obviously I didnt value bet. So I took advantage of him lifting his cards too high for the rest of the night. Can the dealer warn me about this if they notice. I would also like to know at the same time for the dealers at the B&M casino. Is this ok to take advantage or is this cheating and im a POS?