slip through somebody's fingers
slip through (one's) fingers
1. To narrowly avoid being caught, captured, or maintained in custody by one, usually due to cunning or trickery by the one being pursued. The officers very nearly apprehended the suspect, but he slipped through their fingers at the last second. We had the cell guarded by three people, but she still managed to slip through our fingers somehow.
2. To narrowly fail to be attained, achieved, or seized upon by one. I had a chance to be a part of a Broadway musical once, but I was too unsure of myself and the opportunity slipped through my fingers. We've been training too hard to let another championship title slip through our fingers again this year!