Drop beneath the/(one's) radar verb phrase
Ignored or unnoticed by one
Though there are lots of cameras in prison, some prisoners still drop beneath the radar and escape successfully.
No one found out about his scam because he took advantage of his authority to drop beneath the radar.
He dropped beneath the radar and successfully stole a lot of valuable items in the mall.
The verb "drop" must be conjugated according to its tense.
It was often said by a photographer when he would like small children to look at the camera and smile before he took a photo.
When the photographer said “watch the birdie”, all of us looked at the camera and smiled.