Ok, I'm going to start right off by saying that I definitely think it's a possibility, but I'm not "all in" on this being true. It's more of a thought experiment since I don't have any real evidence as of yet, but speculation and hints.
First thing to address: Why does everyone think Pink Diamond was shattered. Because they've been told. So far, the only real eye witness we've met is Eyeball, and in both "Back to the Moon" and "Hit the Diamond" (hmmm could that be a play on words pertaining to this situation or am I just reaching?) it's been shown that Rubies are pretty gullible and not very smart. Eyeball could very well be an unreliable witness even if she doesn't know it. I'm sure she believes that she saw Pink Diamond get shattered by Rose Quartz, but who's to say she wasn't tricked? They miscounted their own numbers and mistook a purple colored Jasper for the real Jasper.
Yellow also mentions in "The Trial" that she was shattered in front of her own court. So where are all of those witnesses? Blue Zircon brings up that Pink's agate, sapphire, and pearl all seemed to miss a giant Rose Quartz just waltzing up to Pink Diamond outside of her palanquin and shattering her. It makes more sense that a Diamond that Pink knew and trusted could get close to her at that point in the rebellion.
WHY WOULD PINK NEED TO BE REMOVED?
There are many reasons and theories as to why any of the Diamonds would have wanted Pink Diamond gone. Blue is shown to be driven by her emotions, and may have done something that she's blocked out. Yellow may have seen the potential for the cluster or some other super weapon in the Earth and Pink stood in the way. Pink may have gotten too fond of her first colony and the humans (hence the Zoo) and could have been perceived as a weak link by White Diamond. Or any combination of the above. We don't have enough information yet.
One thing I do feel pretty certain on is that Yellow Diamond seems to know more about the situation than she is letting on. She may be directly involved, under orders from White Diamond, or just trying to protect Blue Diamond. Or maybe she picked up on what Blue Zircon brought up at the trial eons ago, but doesn't want to believe that a diamond could do that to her own kind. Either way, she knows something.
Maybe it was Rose Quartz in some capacity, and her taking out Pink was made possible by a Diamond because her removal was advantageous to their end goal.
SO WHERE IS PINK DIAMOND?
So if she wasn't shattered, where is this magical mcguffin that could have solved all of our problems centuries ago? I think that Pink Diamond was poofed and bubbled. Maybe it was by Rose Quartz, maybe it was one of the Diamonds. Either way, I don't think she was shattered simply because she CANNOT be shattered.
If we've learned nothing else from this show, we've at least learned 2 things. 1. Major Plot points are foreshadowed throughout the series. 2. Always pay attention to the details.
What do we know about a Rose Quartz gem? It is a stone known for representing love and healing
A Pearl? A decoration used to adorn the "rich" and powerful. Known first and foremost as an object rather than a stone with properties
A Sapphire? Known for truth and loyalty. Shares many properties with a Ruby
When all else fails, without having to do a google search, even with the most cursory knowledge, what is the one thing everyone knows about Diamonds? THEY DO NOT BREAK.
in "The Trial" the only solid fact we get is that Pink Diamond was taken out with a sword. Excluding the possibilities of Diamonds being involved, and just focusing on Rose Quartz. Considering the timeline, when and how Garnet joined the rebellion, and when Bismuth was bubbled, we can guess that the breaking point was invented after Pink Diamond was shattered. This is just a guess, but why would Blue be so quick tempered and even seemingly running the Homeworld front if Pink Diamond was still around. This leaves Rose with her specific gem poofing/non-shattering sword. If this was a new invention that Bismuth made specifically for Rose. It stands to reason that her being able to take out a diamond that easily could be misconstrued as shattering. When, in actuality, Rose merely poofed her and has her bubbled in a safe place. A place that couldn't be gotten to easily or accidentally. Say, a locked chest in a hidden dimension?
On the other side of things; I wouldn't be at all surprised if Yellow, Blue, or White Diamond had the ability to disrupt another Diamond's form without the use of a weapon.
I think that one of the last big twists of the series be the reveal that Pink Diamond was never shattered. How we will get to that twist, we'll just have to wait and see.
What do you think?