3 hens gone broody and now I can't find one

We've been lucky to not have dealt with any extensive broodiness with my sussex for 4 years, but we have been a little lax on the collecting this week or so and now our 3 speckled sussex are all screams and fluff. Two days ago one was MIA but I found her nest deep in some blackberries. Yesterday I found the other in the nest box on a stash of eggs. All 4 were accounted for yesterday, but one is still missing today.

I am telling myself she's probably hunkered deeper in the bramble, but I can't stop worrying. I've done a walk around the neighborhood to look for evidence of an escape or feathers, but nothing. No reports from neighbors or animal control either. Has anyone had a broody hen hide for a couple days while broody?