Actually doing research by asking around, posting the move for people to actually see it, going through old resources to see if anything similar has been posted, waiting for a bit to see if anyone responds.
Searching on Instagram and Reddit for 15 minutes won't get you anywhere.
@NotAceOfClubs I suggest posting the move here, as well as a few other places just to show people. Someone will most probably recognize it if it is an already preexisting move. No one is going to need to show proof, but rather just direct you to another source. You could also hunt around online in archives, though it's a bit trickier with cardistry than it is with magic. With magic, you have great resources such as Conjuring Archive that can describe certain effects in detail and help you figure out whether or not the move already exists.