When you set your clock, make sure it says 20:00. That is 8 pm (assuming all the 3DS clocks are set to military time like the four I own. If you still aren't finding them, go back and make sure you talked to both the rival for battle and the professor. If he's not at the sundial then you should be good.
If the stones still don't appear, check your inventory and Pokemon to see if you may have given it to them.
If they still aren't there, then one of two things.
1)You already collected it and didn't realize it and may hap deleted/sold it.
2)There is an issue with your game. In which case we cannot help you, send a letter to Gamefreak/TPC though they will not do more than say they are sorry.
I've collected all cept one. If you are having trouble then there is an issue with what you are trying to do and you missed a step or aren't following everything 100%. Watch a youtube video on collecting the stones, make sure your time is set correctly. You can tell if it is correct by starting in Ainstar and watching the beam of light go through the crystal and activating the compass thing. If it doesn't activate, you have the wrong time. Once it activates go to each exact location in one of the youtube videos. They should be there unless you already collected them.
Well thank you all for the help so far. I will take your advice and set my 3DS clock to military time and check it tomorrow, although I strongly doubt that they clocks are set to military time, it really doesn't look like mine is, and if it is than that's very deceiving, it should say that it's military time if that's the case.
I have checked my inventory and my Pokemon and this is how I know. For instance, my Garchomp does not have a Garchompite or even the option to Mega evolve, and there is no Garchompite in my inventory, nor is it in its location on Victory Road near the Stone Tower, I checked several times and it's simply not there, and for an even better example, I don't even have Gyrados in that I haven't been able to evolve my Magikarp yet, and yet I could not find the Gyrados mega stone in its location at the waterfalls in that one particular city, so unless you're right about the military time, (which would seem unlikely to me, although you say you have four 3DSs that are set to military time (I'm not sure why you'd have four game systems, but that's just me)), there's something very wrong.
If there's an issue with my game, are you sure GameFreak would be able to do nothing more than apologize? I'd sure hope they'd do more than that being that it wouldn't be my fault, but there's if it really is a default in the game and I'm the one that paid for it.
And are you sure it's not possible that no one could hack into my profile and steal all the mega stones before i could get to em via the internet connection?
EDIT: Ok, I just checked it (Checked it a little earlier than tomorrow ;)), and that was definitely the resolution. The clocks are set to military time, I don't know why, but that's very decieving, don't know how anyone would know that off hand. I mean, the game guide websites don't even mention this!! I would love to know who the **** would ever know that?!?! Who the **** even ever lives in military time other than people who are actually in the military?
Anyways, thank you very much for the help, it is much appreciated! :)
Ok, now that I've got the whole mega stone search mystery sorted out, new question;
WTF? Why is the Aggronite only available in Y and the Tyrantitarite available only in X? Plus, Tyranitar is only found in Y while Aggron is only available in X? WTF? What's with the switch up?
