Catching seeds,,,

Hello,,looking for advice,,

i have some Himalayan plants outdoors,(guerilla) just growing for seed to acclimatise year on year,,,

As these are very sativa type buds , the seeds will fall from the buds easily when ripe and as I cant be there due to location and work etc,,I am thinking of some kind of muslin bag to tie on the end of some branches to catch falling seeds,,,as its really the ripest ,earliest seeds that I want ,,the whole point of the grow is for the seeds,,and dont want to loose them to the wind,,weather etc,,
First thought about putting a fabric sheet on the ground to help findfallen seeds,,but then thought about bags,,similar idea to pollination bags,,

could this work ? Or will it invite mold , any suggestions for type of material to use/make bags from ?

thanks

Window screen? Not sure but screen will atleast have airflow and drain well