@blueandgreen, I have experience with one state only, not Florida, but my guess is the letter of completion, if it was actually required, was required in order for the school board/state agency to monitor compliance with state compulsory eduction requirements in place up till age 17 or so.
It is only my opinion, but I doubt it will affect your college application unless a school specifically requires an official state-recognized diploma. You can find out for sure on each school’s website. Even in that case, I doubt they will request to see a diploma if your homeschool transcript and any dual-credit transcripts are convincing as to the academic rigor and thoroughness of your work. But, if they ask, you will be compelled to answer honestly.
I don’t want to frighten you, but I assume you are a junior, so consider that the school board bureaucracy may yet catch up and contact your parents about your education. With the little I know about your situation, I don’t even have an opinion on how you should deal with that possibility. Perhaps an anonymous call to your local school board would give you an idea of how to proceed.