The same thing happens here, it is a parasitic wasp -

https://www.canr.msu.edu/news/the_grass_carrying_wasp_a_solitary_wasp_that_builds_nests_in_unusual_places

mystery solved. i read the article & it sounds like i wiped out the next generation. there were no signs of eggs or larva in the debris but the article says they emerge in the spring. maybe this was last years nest never saw them flying around either. this stuff was packed in so tight that it was difficult to get it out. it's like they used a hydraulic press. insect are wondrous creatures.

CORECTION-i dug thru the debris & found empty cocoons with the exoskeletons of small crickets so these were from a previous year. red headed mud dauber wasps do the same thing. if you break open their mud nests you'll find stunned spiders waiting to be eaten by hatchings wasps.