There are other possibilities too.
1) You’re giving your opponent information based on in what order and how quickly you lay your gravestones. If you seem over-eager, maybe that’s the one that gets destroyed.
2) Your opponent is picking what gravestone to destroy based on what lane it’s in, and what (s)he is trying to protect.
3) Your opponent only drew the graveyard hate when you drew the card you needed. Alternatively, your opponent had the hate all along, but chose to develop board during previous turns.
4) Your opponent got lucky on two occasions. It happens.
I don’t know under what circumstances your opponent is “guessing right.” If this is a mixed-up gravedigger scenario, there is even a chance an already-played Zombie appears as a cartoonishly large gravestone... a game glitch that I’ve seen before. (I don’t know exactly what triggers it.)
But Daalnni is absolutely right: I don’t play plants as often as zombies, but unless you have a whole lot of brains floating during the trick phase, it isn’t too hard to predict what’s under a stone based on the zombie types being played and the brains available.
Simple example: if I’m playing The Smash, and he dropped a Arm Wrestler turn 1 and then a Stone on 2, I would have to be crazy to play my Double Sunflower.
