The referee's whistle does not have to be blown to re-start play on all kicks. Only on certain restarts does it have to be blown. Free kicks do not necessarily require a whistle to signal the restart. It was a heads-up play by Messi to take the kick before anyone was expecting it.
Actually, I believe it is the taa marbuuTah that would be the 29th letter, but is often left out, due to both its similarity to the haa in shape and its lack of an actual pronunciation in most words. (just my opinion, I am still learning myself)
The referee's whistle does not have to be blown to re-start play on all kicks. Only on certain restarts does it have to be blown. Free kicks do not necessarily require a whistle to signal the restart. It was a heads-up play by Messi to take the kick before anyone was expecting it.