Firstly, it's IBTL (In Before the Lock), not ITBL.
These are useless posts which in now way contribute to the forum.
Your thread title asks what happens if you don't know you've posted one?
Well, first off - don't post one, ever. A two day ban will heading your way if you do.
To find if you've posted one in the past, use the search feature and search for your posts by you, with IBTL as the criteria. This should return any if you've posted them in the past.
To read more about the reasoning behind banning IBTL posts and the consequences, see
this thread. It explains it all.
I hope this answers your questions, you don't seem to be that clear on what you want.
