I felt that dude however your question is answered already. Even on off topic thread which is the simpliest way to increase your post as a beginner (for me), they deleted unrealable post. I understand its quite frustrating when ur post is deleted on off topic like what now? I just answered a question? But whats important ks it should relate to the OP. But dont feel bad about it, we all gone through that.
This is something i have experienced in this forum many times. Most of the times i don't have the slightest idea why something gets deleted, as they don't write even a single word for the reason (except one time the mod made a mistake and told me to re-post it), so one could learn to avoid making the same mistake (whatever it was) again...
Sometimes it is guessable, but often its not. I feel that reporting to admin would bother Theymos too much so i refrain from doing it, but sometimes its tempting because it can be so random when it comes...
I guess this is a "who watches the watchers" kind of situation, but its not the end of the world. I just let it go and move on.