Help! Blue Tits Abandoned.

We have Blue Tits nesting in our garden hose reel. It's a boxed in type. We noticed the parents coming back with grubs so assumed they had hatched. We haven't seen the parents at all since yesterday and that was only once. There sounds like there is a chick inside. I think it has fallen to the bottom of the hose reel and is stuck. 

What shall I do? I'm thinking of taking the reel apart and seeing if I can save the chick.