I knew what you meant and I guess in a manner of speaking it is unlucky. But it's not as if the helmet actually helped him catch the ball, that's not the real reason the rule was put in there, he just nearly got an unintended free life because of it.I think the rules are the ball is dead (according to Michael Holding), Bairstow was unaware it had hit the grill, that's why I used the word unlucky.
It's just one of those phrases that people use all the time that annoys me, like when a winger miss hits a cross and it hits the back post but doesn't go in. People say he's unlucky, when really he just was nearly incredibly lucky. Not getting incredibly lucky isn't being unlucky. (I know this is a bit of a rant, but my brother is one of those people that declares everything unlucky and it annoys the crap out of me!)