I'm worried that I will be falsely accused of plagiarism (business coursework gcse)

I posted my gcse course work essay on the student room, as a thread so people could suggest improvements. The student room somehow deleted this post and I can't find it if I search for it in google (this isnt a problem), but I'm worried that when the exam board try to detect plagiarism this deleted thread will somehow come up and they will think I cheated, even though I wrote the post myself. Ive copied my work into plagiarism checkers and the checkers say that my works 100% genuine and original, but I'm worried that the checker I used wont be as advanced as the one the exam board will use. Help! and if they say my work is copied how can I prove that it is actually my work?