There is no real criteria regarding who uploads it, unless the group specifically says that only their members are allowed to upload or something similar.
It could have been that your chapter was on moderation list waiting to be moderated and in the meanwhile someone else with contributor status uploaded, so it ended up in your chapter being deleted because the one from contributor was automatically approved.
If not, then your upload shouldnt be deleted, unless there was something wrong with it(which I dont know, I was not the one who removed it).
The person who uploaded it was a Member. So I don't know what was wrong.
The group's delay policies don't say anything.
I did receive a rather suspicious visit from KidCongo last night, however.....