There's also the possibility that the leak was from people or activities associated with the lab but not from inside the lab. For example, they hire some local people to go and fetch some more bats from the bat caves in another province. Those people drive to the other province in their white van, go into the caves, inhale lots of guana, grab some bats, drive back to the Wuhan lab, hand over the bats, then drive into central Wuhan to get a coffee and see if there are any good offers at the wet market. (OK, they probably wouldn't actually be infectious straight afterwards, but they're local people so they might visit the market next week, too.)