THEORY: The person who sent the player the "Find the Flower" letter is Cole Vaughn.

for anyone who doesn't already know, Cole Vaughn is a shelf keeper and minor character introduced in the "Break Time" VHS tape in Chapter 4, as well as in the four journal pages he left behind in the factory. it's established in these pages that he figures out the secrets that Playtime Co. is hiding from their workers, breaking into the archives in order to obtain this information.

but, did anyone ever take into account HOW somebody would be able to send the Poppy Commercial Tape to us, and how they would be able to set up these VHS tapes and bits of information around the factory? not to mention the use of "WE'RE still here" in the Find the Flower letter. whoever this person is, they are, or were, an employee, one that still remains at the factory with the rest of the workers. this employee would also need to have access to these tapes and documents, as well as have access to the address of our player in order to send the letter.

if this person IS Cole, it would definitely make more sense than other characters. unlike the player, Cole was confirmed to have been at the factory during the Hour of Joy, being dragged by the toys to the cells with the other employees. this, as well as having access to all of the archives, means he could have sent the player the Find the Flower letter, along with the Poppy Commercial Tape. Cole also seems extremely straightforward in his journal pages about wanting to destroy everything having to do with Playtime's past, which gives him the incentive to send the letter in the first place. and finally, since our player character is in fact an employee as well, Cole could have possibly known us before the Hour, which explains why he knows where to send the letter to.

thanks for reading, if you did- this is one of my first poppy playtime theories!! so if you see any flaws in my logic, do point them out, i need feedback.