It certainly could be, especially if you’re not doing anything wrong. But if a government pries that much, you’d maybe be painting a target on your back by inventing a new language. You could also use an existing language that is hard to translate and learn, and isn’t well known. Like Ithkuil
You’ve also ruled out TH by knowing one is heads. So the only possibilities are HT and HH. Is that not 50/50?