I cannot believe any site, especially Pokerstars would do something like that, I myself have had occasions where I felt I had the hand in the bag, but the River card steals the pot away by giving me a set but making the other players hand into a straight or flush.
It has happened to me numerous times, but when I study the history I find I was wrong and he had me beat, I have also been on the receiving side sometimes, once all-in with 8/8 against A/A I hit a miraculous 4 card flush on the River after the flop had given both of us a set with A,10,8, then the turn gave us a 6 and finally a 2 on the River. 4 of the cards were Hearts and I held the 8 of Hearts in my hand, so I sucked out on him, but that happens, That's Poker!
I think if you looked at the History after a hand is over, you will find that you missed something and what you read was wrong. It is easily done.
When the fun Stops, STOP!